In this her fourth trip to federal court and her second appearance before this court, the plaintiff-appellant, Agnes Nilsen, seeks once more an opportunity to demonstrate the merit of her charge that the defendant-appellee, the City of Moss Point, Mississippi, discriminated against her unlawfully. Her first three suits, filed under Title VII, 42 U.S.C. § 2000e, were dismissed for various deficiencies, before Nilsen presented any evidence of discrimination. Now, Nilsen brings a fourth suit, attempting to establish liability under the fourteenth amendment and the Civil Rights Act of 1871, 42 U.S.C. § 1983. Although the litigation raises complex and troubling issues concerning the preclusive effect of prior actions, we are persuaded that, in the special circumstances of this case, the plaintiff must at last have her day in court, where she will be put to her proof on both the timeliness and the merit of her allegations.

Nilsen applied for a position as a firefighter with the Fire Department of the City of Moss Point in July 1974. When her application was rejected, she filed a charge of sex discrimination against the city with the Equal Employment Opportunity Commission in August 1974. Conciliation efforts failed, and Nilsen received a right-to-sue letter on June 5, 1975. In July 1975, she filed suit (Nilsen I ) in the United States District Court for the Southern District of Mississippi against the Chief of the Moss Point Fire Department and the Chairman of the Moss Point Civil Service Commission. That suit was dismissed because the defendants were not employers and were not named in the EEOC charge. The trial court specified that the dismissal "was without prejudice to the plaintiff to sue the proper party".1

On January 13, 1976, Nilsen filed a suit (Nilsen II ) against the city, certain individuals, and certain departments of city government. That complaint alleged substantially the same facts as did the complaint in Nilsen I. On July 21, 1976, Nilsen filed her third suit (Nilsen III ) against the city, the Fire Department, the Civil Service Commission, and the Mayor. It arose from a second EEOC charge that Nilsen filed on November 15, 1975, alleging continuing discrimination. On that charge, Nilsen received a right-to-sue letter on March 23, 1976. Nilsen II and Nilsen III were consolidated for consideration of the defendants' motion for summary judgment. That motion was based on the theory that Nilsen brought Nilsen II more than ninety days after the issuance of her right-to-sue letter and brought the EEOC charges leading to Nilsen III more than 180 days after she became aware of the facts supporting her charge. Title VII requires the timely invocation of EEOC conciliation procedures and of the judicial process: a Title VII plaintiff must file charges with the EEOC within 180 days of learning of his claim, 42 U.S.C. § 2000e-5(e), and, if conciliation efforts fail, and the EEOC, instead of bringing suit, issues a right-to-sue letter, the plaintiff must file suit within ninety days of receipt of that letter, id., § 2000e-5(f)(1). After settlement efforts by the parties here failed, the court scheduled a hearing on the motion for summary judgment on June 9, 1977. On June 15, 1977, before decision on the motion for summary judgment, Nilsen moved to amend her complaint to include a claim for relief under 42 U.S.C. § 1983, based on the same alleged discrimination. Not until November 28, 1978, did the magistrate file his recommendations in the consolidated cases, and on February 12, 1979, the court adopted those recommendations. The district court denied Nilsen's motion to amend and granted the defendants' motion for summary judgment on the original complaint, reasoning that the plaintiff had failed to meet the timely filing requirements of Title VII.2 Nilsen took an appeal, and a panel of this court affirmed both the denial of leave to amend and the grant of summary judgment. Nilsen v. City of Moss Point, 5 Cir. 1980, 621 F.2d 117.

Nilsen, undaunted, filed yet another suit (Nilsen IV ) on August 29, 1980, against Moss Point, seeking to assert the constitutional claims that were the subject of her proposed amendments in Nilsen II/III. The city moved for summary judgment, and the district court granted the motion on two grounds. First, the court held that the judgment in Nilsen II/III barred Nilsen IV under the doctrine of res judicata. Second, as an alternative ground, the court held that the denial of leave to amend in Nilsen II/III entailed determinations of delay and prejudice tantamount to a finding of laches. Since Nilsen was collaterally estopped to relitigate those questions, the court reasoned, her § 1983 claim was, as a matter of law, barred by laches.

On this appeal, Nilsen urges that Nilsen IV is not res judicata for two reasons. First, she contends, the summary judgment in Nilsen II/III was premised on the failure to meet "jurisdictional" timely filing requirements, and a judgment that a court lacks subject matter jurisdiction is not res judicata as to the merits of the claim. Second, Nilsen argues, Title VII and § 1983 are not the "same cause of action", so a judgment in a Title VII suit, even if on the merits, would not bar a subsequent § 1983 suit on the same facts.

Next, Nilsen attacks the alternative ground for the result in the district court. Again, she presents several arguments, any one of which, if meritorious, would undermine this ground for the district court's holding. First, she asserts that her complaint requests both legal and equitable relief, so, instead of laches, the statute of limitations governs-here, the Mississippi catch-all limitations provision, granting a six-year period. Second, even if laches does govern, she contends that the Nilsen II/III court did not find prejudice, a necessary condition for laches. Finally, she argues that the degree of delay and prejudice that justifies a denial of leave to amend under rule 15(a), Fed.R.Civ.P., does not equal the degree necessary to support a finding of laches.

Even more complex than the procedural history of this litigation are the issues now presented to us for decision. Fortunately, our disposition of the case permits us to pretermit some of the vexing problems raised. The resolution of the remainder, however, is inescapable, and our resolution requires us to reverse the judgment of the district court.

Res judicata will bar an action if there has been a prior judgment on the merits on the same cause of action in a suit between the same parties. See generally Kemp v. Birmingham News, 5 Cir. 1979, 606 F.2d 1049, 1052. The trial judge here concluded that the judgment in Nilsen II/III was "based upon a statute of limitations" and therefore was a decision on the merits. Further, he concluded that Nilsen's Title VII claim and her § 1983 claim, which concededly arise out of a single occurrence, are the same cause of action.

A dismissal for lack of subject matter jurisdiction is not a bar to a later action brought in a court of competent jurisdiction on the same claim. See 5 C. Wright & A. Miller, Federal Practice and Procedure § 1350 (1969). At the same time, a dismissal based upon the statute of limitations will bar claims that, although themselves still timely, are part of the same cause of action as the previously asserted time-barred claim. See Mervin v. FTC, D.C.Cir.1978, 591 F.2d 821 (per curiam); Cemer v. Marathon Oil Co., 6 Cir. 1978, 583 F.2d 830 (per curiam). The question confronting the trial judge, then, was which of these rules governs the dismissal of a Title VII claim for failure to meet the timely filing requirements. The plaintiff argues that these requirements are jurisdictional in the res judicata sense and that, even if under current law they are not jurisdictional, the courts in Nilsen II/III characterized their decision as a dismissal for lack of jurisdiction, and that characterization is the law of the case.

The court in Nilsen II/III stated that the unfulfilled requirements were "jurisdictional", and this court used the same language in affirming. Nilsen II/III, 621 F.2d at 121. But the term "jurisdictional" does not carry the same meaning in every context in which it is employed. Thus, for instance, flaws that would not leave a judgment vulnerable to collateral attack may nonetheless be considered jurisdictional for res judicata purposes. Costello v. United States, 1961, 365 U.S. 265, 285, 81 S. Ct. 534, 544, 5 L. Ed. 2d 551; see generally 9 C. Wright & A. Miller, Federal Practice and Procedure § 2373 (1971).3 Since "jurisdictional" does not carry a single unvarying meaning, we reject the plaintiff's argument that the characterization of the requirement adopted in Nilsen II/III is the law of the case. The court there was not considering jurisdiction in the res judicata sense. On the contrary, the court was considering only whether it could continue to entertain the action. See Reeb v. Economic Opportunity Atlanta, Inc., 5 Cir. 1975, 516 F.2d 924, 927. The Nilsen II/III court's discussion of the possibility of equitable tolling, 621 F.2d at 120-21, shows that its view was that the requirements are not jurisdictional in every sense of the word.

The Title VII requirements and the parallel requirement in the Age Discrimination in Employment Act, 29 U.S.C. § 626(d)(1), have sparked a great deal of litigation seeking to clarify in which senses they are jurisdictional,4 leading the Supreme Court to grant certiorari to decide the question. After the district court's decision in this case, the Court held in Zipes v. Trans World Airlines, Inc., 1982, --- U.S. ----, 102 S. Ct. 1127, 71 L.Ed.2d ----, that the requirement of filing with the EEOC is subject to waiver, estoppel, and equitable tolling. Of course, as we have noted, "jurisdictional" need not have the same meaning in every context, so the characterization of the timely filing requirements for purposes of waiver, estoppel, and equitable tolling does not necessarily govern the characterization of these requirements for purposes of determining the res judicata effect of a judgment. We have found no authority on that precise point, and the parties have cited us none.5 Much of the reasoning of the Zipes opinion, though, applies not only to the question whether the requirement is jurisdictional for the purposes of waiver, estoppel, and equitable tolling but also to the question whether it is jurisdictional for the purpose of res judicata. See id. --- U.S. at ----, 102 S. Ct. at 1130. We are convinced, however, for other reasons, that res judicata does not bar Nilsen's action, so we need not finally resolve this question.6

Res judicata and the related doctrine of collateral estoppel further the salutary goals of judicial economy, avoidance of inconsistent judgments, and repose. The doctrine necessarily operates harshly, for it precludes assertion of potentially meritorious claims without any consideration of their merit. Yet that harshness is not without limits. The rules for the application of res judicata are targeted at litigants who are "at fault" either in the sense of having failed to persuade a tribunal of the merit of their claims or in the sense of having slept on their rights-the litigant who has already asserted the arguments he wishes to assert and has received an adverse judgment or the litigant who failed to assert the arguments when he should have done so. The former situation does not arise here: Nilsen has never presented the merits of her § 1983 claim in court. Instead, the problem arises because of the possibility of characterizing Nilsen as a litigant who failed to assert her § 1983 claim in a prior action in which she should have done so. We cannot accept that characterization, though, for Nilsen attempted to assert her claims by amending her complaint. The rule against splitting causes of action is designed to encourage the litigant to raise in a single suit all his claims that bear a certain relationship to the transaction at issue. But the rule has no function if the procedural system does not permit the litigant to raise all of those claims in one proceeding. Thus, for instance, the rule against splitting a cause of action operated on a different definition of "cause of action" before the merger of law and equity, when the system did not permit a litigant to pursue his legal and equitable claims in a single proceeding. See Developments in the Law-Res Judicata, 65 Harv.L.Rev. 818, 824 n.33 (1952). As the American Law Institute explains, "Equating claim with transaction ... is justified only when the parties have ample procedural means for fully developing the entire transaction in the one action going to the merits to which the plaintiff is ordinarily confined." Restatement (Second) of Judgments § 61, comment a at 141 (Tent. Draft No. 5, 1978). See Melaro v. Mezzanotte, D.C.Cir.1965, 352 F.2d 720, 722.

The operation of the rules of res judicata on claims over which a federal court declines to exercise pendent jurisdiction provides a useful analogy. When a single transaction or occurrence gives rise to some claims within the subject matter jurisdiction of the federal courts as well as some state law claims with no independent basis for federal jurisdiction, the federal courts have discretion to exercise pendent jurisdiction over the state law claims. United Mine Workers v. Gibbs, 1966, 383 U.S. 715, 86 S. Ct. 1130, 16 L. Ed. 2d 218. But if the federal court declines to exercise jurisdiction over the state law claims, in fairness, the claimant must have the opportunity to raise those claims in state court. See Bowers v. DeVito, N.D.Ill.1980, 486 F. Supp. 742, 744 n.3; Note, The Res Judicata Implications of Pendent Jurisdiction, 66 Cornell L.Rev. 608, 614 & n.26 (1981).7 Similarly, when the court in Nilsen II/III declined to exercise its discretion to permit the amendment of the complaint, fairness requires that Nilsen be given an opportunity to raise those claims in a second proceeding.8

Nilsen cannot be barred on the theory that she should have brought her § 1983 claim in Nilsen II/III when she attempted to do so, and leave to amend was denied.9 She did what the rule against splitting causes of action encourages her to do: she attempted to consolidate all her claims in one proceeding. It would be unduly harsh and would extend the rule against splitting well beyond its rationale to apply it to a plaintiff who was not permitted to bring her claim in the first proceeding.10

We find support for our holding in a number of Title VII and § 1983 decisions. The Supreme Court, in denying preclusive effect to an arbitral determination in a later Title VII suit in Alexander v. Gardner-Denver Co., 1974, 415 U.S. 36, 94 S. Ct. 1011, 39 L. Ed. 2d 147, was motivated at least in part by the failure of the arbitration proceeding to provide an opportunity to present Title VII claims.11 The lower courts too offer support. In Ludwig v. Quebecor Dailies, Inc., E.D.Pa.1980, 483 F. Supp. 594, the plaintiff had brought an action little more than a month after her discharge, asserting claims under §§ 1981, 1983, 1985(3), and 1986. Shortly thereafter, she filed a charge with the EEOC. Her suit was dismissed, and the next day she filed a Title VII suit. The court permitted the Title VII action to proceed because the plaintiff had not received her right-to-sue letter from the EEOC until after the dismissal of the first action; thus, at the time of the first action, the Title VII claim was not a ground of recovery that could have presented in the first action. Similarly, Nilsen's § 1983 claims could not have been presented in her first action by virtue of the court's refusal to entertain those claims in that action. In such circumstances, we refuse to give preclusive effect to Nilsen II/III on Nilsen's § 1983 claims.

As an alternative ground for its decision, the district court ruled that the denial of leave to amend collaterally estopped Nilsen to relitigate the issue of laches and that laches was a complete defense to the § 1983 claim.

Nilsen argues first that, since she requests both legal and equitable relief, the statute of limitations12 rather than laches governs the timeliness of her claim.13 Several cases hold that when a § 1983 action is brought for both damages and equitable relief, the statute of limitations, and not laches, controls both the legal and equitable part. Mizell v. North Broward Hospital District, 5 Cir. 1970, 427 F.2d 468 (on petition for rehearing); Swan v. Board of Higher Education, 2 Cir. 1963, 319 F.2d 56, 59 n.5; Graffals Gonzalez v. Garcia Santiago, D. P.R.1976, 415 F. Supp. 19, aff'd, 1 Cir. 1977, 550 F.2d 687; Cestaro v. Mackell, E.D.N.Y., 429 F. Supp. 465 aff'd without op., 2 Cir. 1977, 573 F.2d 1288; Needleman v. Bohlen, D.Mass.1974, 386 F. Supp. 741, 749; cf. Saffron v. Department of the Navy, D.C.Cir.1977, 561 F.2d 938 (suit for backpay, damages, and reinstatement in government employment), cert. denied, 1978, 434 U.S. 1033, 98 S. Ct. 765, 54 L. Ed. 2d 780; Baker v. F & F Investment, 7 Cir., 420 F.2d 1191, 1193 (§ 1982), cert. denied, 1970, 400 U.S. 821, 91 S. Ct. 42, 27 L. Ed. 2d 49; Morgan v. Koch, 7 Cir. 1969, 419 F.2d 993, 996 (Securities Exchange Act) (dictum). Most of these cases, and in particular the case in this circuit, seem to assume that laches provides a longer period than does the statute of limitations.14 Cf. Note, Laches in Federal Substantive Law: Relations to Statutes of Limitations, 56 B.U.L.Rev. 970, 976-81 (1976) (considering running of statute of limitations as a factor in determining whether laches has run). Indeed, the Supreme Court opinions often cited for the proposition that the statute of limitations governs both legal and equitable relief in cases of concurrent jurisdiction stated only that equity will withhold relief when the statute of limitations on the analogous legal claim has run. Cope v. Anderson, 1947, 331 U.S. 461, 464, 67 S. Ct. 1340, 1341, 91 L. Ed. 1602; Russell v. Todd, 1940, 309 U.S. 280, 289, 60 S. Ct. 527, 532, 84 L. Ed. 754. Thus, they considered only the case in which laches provides the longer period. When dealing with other statutes, this circuit has stated that, in a proper case, laches could apply to a mixed federal claim. United Transportation Union v. Florida East Coast Railway Co., 5 Cir. 1978, 586 F.2d 520, 524-25 (Railway Labor Act); United States v. Georgia Power Co., 5 Cir. 1973, 474 F.2d 906, 923 (Title VII); see also Tobacco and Allied Stocks, Inc. v. Transamerica Corp., 3 Cir. 1957, 244 F.2d 902. Consequently, we consider still open the question whether laches will bar all relief in a mixed § 1983 claim when the statute of limitations has not run.

The key concern in selecting a rule for mixed claims was expressed well by the Ninth Circuit in Royal Air Properties v. Smith, 9 Cir. 1962, 312 F.2d 210, 214: "The applicable period of limitations should not depend 'on the turn of a word fixed by a plaintiff at the pleading stage.' " See Swan v. Board of Higher Education, 2 Cir. 1963, 319 F.2d 56, 59 n.5; Tobacco and Allied Stocks, Inc. v. Transamerica Corp., D.Del.1956, 143 F. Supp. 323, 326-27, aff'd on another point, 3 Cir. 1957, 244 F.2d 902. Thus, a claim should be treated as one requesting mixed relief if mixed relief is available, regardless of whether the plaintiff actually requests more than one type of relief. A plaintiff should not be deterred from adding a request for injunctive relief to his claim for compensatory damages because he fears that the addition will leave his claim for damages subject to a short laches period rather than to a longer period provided by the statute of limitations. When we consider this reasoning along with settled precedent establishing that laches can bar an equitable claim but only the statute of limitations will bar a legal claim,15 we think that although the equitable part of a mixed claim can be barred by laches, the legal part will be barred only by the statute of limitations.

Therefore, Nilsen's legal claims survive the city's assertion of a laches defense. With respect to the equitable claims, which may be barred by laches, we must still decide whether the laches period has run as a matter of law.

The district court reasoned that the determination of delay and prejudice that supported the denial of leave to amend in Nilsen II/III establish as a matter of law that laches has run. We agree with the appellee that, in general, both prejudice and delay enter into the decision of a motion for leave to amend, see, e.g., Dussuoy v. Gulf Coast Investment Corp., 5 Cir. 1981, 660 F.2d 594, 598-99; Griggs v. Hinds Junior College, 5 Cir. 1977, 563 F.2d 179 (per curiam); 6 C. Wright & A. Miller, Federal Practice and Procedure § 1484 (1971); Note, Laches in Federal Substantive Law: Relations to Statutes of Limitations, 56 B.U.L.Rev. 970, 971 (1976);16 and that the Nilsen II/III courts found both elements. 621 F.2d at 122. We do not, however, agree that the standards for delay and prejudice necessary to establish that denial of leave to amend is appropriate automatically establish that laches has run.

We have not found any cases exploring the relationship between the rule 15(b) standards and the laches standards.17 It is clear that the basic concerns are the same. Rule 15 requires the court to consider such factors as undue delay, bad faith or dilatory motive on the part of the movant, repeated failures to cure deficiencies by previously allowed amendments, and prejudice to the opponent. See, e.g., Foman v. Davis, 1962, 371 U.S. 178, 182, 83 S. Ct. 227, 230, 9 L. Ed. 2d 222, 226; Dussuoy v. Gulf Coast Investment Corp., 5 Cir. 1981, 660 F.2d 594, 598. Laches requires an unexcused delay, with undue prejudice to the party against whom the claim is asserted. See, e.g., Environmental Defense Fund v. Alexander, 5 Cir. 1980, 614 F.2d 474, 478; Avondale Shipyards, Inc. v. The Vessel Thomas E. Cuffe, E.D.La.1977, 434 F. Supp. 920, 932. Both rules then are concerned with preventing a claimant from asserting a claim in a time or manner that is inequitable to the party against whom it is asserted while also protecting claimants whose failure to raise the claim earlier is excusable or nonprejudicial. The language of the cases provides us little guidance in comparing the two standards. The different roles of the two standards in the procedural system, however, convince us that they are not necessarily identical. A denial of leave to amend need not mean that the claim sought to be asserted will never be heard in any court, as would a determination that laches had run. For instance, at the beginning of an action, a plaintiff is free to join any claims that he may have against the defendant regardless of whether they are factually related. Fed.R.Civ.P. 18(a). If he attempts to amend to include an unrelated claim on the eve of trial, the district court would be justified in denying leave to amend, upon a finding of delay and prejudice. But the denial does not bar the unrelated claim forever; it merely tells the plaintiff that he has chosen the wrong forum or time to assert it. Given this functional difference, the rule 15 standard in such a case should not be as strict as the laches standard.

When the claim asserted in the proposed amendment is so closely related to the subject matter of the action that, absent the attempt to amend, res judicata would bar the claim as part of the "same cause of action", we see some appeal to a rule that the rule 15 standard must reflect the rigor of the laches standard; indeed, were we confronted with a motion to amend under rule 15 in such a situation, we would hesitate to deny leave without applying the laches standard, for fear that the denial of leave to amend would later be given res judicata effect. See Dussuoy, 660 F.2d at 600 n.3. But we cannot hold with any certainty that that was the view of the Nilsen II/III court, for two reasons. First, the rule 15 standard may in some cases allow a limited discretion to the trial court to deny leave to amend to include a transactionally related claim even if laches has not run. Second, the judge faced with the motion to amend has an alternate means of dealing with the motion that reaches precisely the result of disposing of the claim forever: he can permit the amendment and grant judgment on the pleadings or summary judgment, dismissing the claim as untimely.18 Indeed, in this case, the defendant urged the Nilsen II/III court to dismiss or grant summary judgment (although on other grounds) if it chose to permit the amendment. Given that the court had that unambiguous option available to it, we refuse to render a denial of leave to amend unambiguous well after the fact by holding that it bars later litigation of the claim. When a holding depends on ambiguous grounds, neither ground is the subject of collateral estoppel. Melaro v. Mezzanote, D.C.Cir.1969, 352 F.2d 720, 721 n.2.

We hold, therefore, that Nilsen II/III does not bar the claims asserted now. Laches may bar the equitable relief sought, although the question of laches is a factual one that cannot be resolved at this stage of the proceeding; the plaintiff is not estopped on the questions of delay and prejudice. The survival of Nilsen's claims for legal relief is governed by the Mississippi statute of limitations. The case is REVERSED and REMANDED for further proceedings consistent with this opinion.