Opinion of the Court make a significant legal difference. To say this is not, as the concurrence claims, to advocate a "mix-and-match" statute of limitations theory. Post, at 200, n. 3. Rather, it is to recognize that the Clayton Act's express statute of limitations does not necessarily provide all the answers. We shall, at the very least, wait for a case that clearly presents these or related issues, providing an opportunity for full argument, before we attempt to resolve them. Finally, the Klehrs have asked us to review the Eighth Circuit's application of its rule in this case. Doing so would involve examining an evidentiary record of several thousand pages to determine the validity of the independent conclusion of each of two lower courts that the Klehrs should reasonably have discovered the silo's flaws before 1989 (and that a reasonable factfinder could not conclude to the contrary). That conclusion is highly fact based, depending not only upon how much mold the Klehrs noticed in their silage and when, but also upon such matters as the effect of the Klehrs' failure to consult the herd performance records they were continuously sent, and whether their having done so would have led them to tell veterinarians a more revealing story, to question Harvestore's representatives more fully, or to investigate the silo sooner. See 87 F. 3d, at 234. We have no reason to believe that there is any very obvious or exceptional error below. And our writ of certiorari commits us to decide only the purely legal question whether or not a claim accrues "where the Respondent continues to commit predicate acts" in the 4-year period immediately preceding suit. Pet. for Cert. i. We have answered that question in Part II-A. And we shall not go beyond the writ's question to reexamine the fact-based rule-application issue that the Klehrs now raise, and which the Eighth Circuit decided in Harvestore's favor. III Our writ of certiorari contained one further question, namely, whether Opinion of the Court "affirmative continuing acts of fraud . . . coupled with active cover up of the fraud, act to equitably toll the statute of limitations... whether or not Petitioners have exercised reasonable diligence to discover their claim." Ibid. (emphasis added). This question refers to the doctrine of "fraudulent concealment," which some courts have said "equitably tolls" the running of a limitations period, see, e. g., Grimmett, 75 F. 3d, at 514, while other courts have said it is a form of "equitable estoppel," see, e. g., Wolin v. Smith Barney Inc., 83 F. 3d 847, 852 (CA7 1996). Regardless, the question presented here focuses upon a relevant difference among the Circuits in respect to the requirement of "reasonable diligence" on the part of the plaintiff. Some Circuits have held that when a plaintiff does not, in fact, know of a defendant's unlawful activity, and when the defendant takes "affirmative steps" to conceal that unlawful activity, those circumstances are sufficient to toll the limitations period (or to "estop" the defendant from asserting a limitations defense) irrespective of what the plaintiff should have known. See, e. g., id., at 852–853. Other courts have held that a plaintiff who has not exercised reasonable diligence may not benefit from the doctrine. See, e. g., Wood v. Carpenter, 101 U. S. 135, 143 (1879); Bailey, 21 Wall., at 349-350; J. Geils Band Employee Benefit Plan v. Smith Barney Shearson, Inc., 76 F. 3d 1245, 12521255 (CA1 1996) (diligence required for fraudulent concealment under federal law); Urland v. Merrell-Dow Pharmaceuticals, Inc., 822 F. 2d 1268, 1273-1274 (CA3 1987) (same with respect to Pennsylvania law); see also 2 Corman §9.7.1, at 56-57, 60-61, 64-66. We limit our consideration of the question to the context of civil RICO. In that context, we conclude that "reasonable diligence" does matter, and a plaintiff who is not reasonably diligent may not assert "fraudulent concealment." We reach this conclusion for two reasons. First, in the related antitrust context, where the "fraudulent concealment" doc Opinion of the Court trine is invoked fairly often, relevant authority uniformly supports the requirement. Professor Areeda says, for example, that “[t]he concealment requirement is satisfied only if the plaintiff shows that he neither knew nor, in the exercise of due diligence, could reasonably have known of the offense." 2 Areeda ¶ 338, at 152; see also I. Scher, Antitrust Adviser § 10.27, p. 10-62 (4th ed. 1995). We have found many antitrust cases that say the same, and none that says the contrary. See, e. g., Conmar Corp. v. Mitsui & Co., 858 F.2d 499, 502 (CA9 1988), cert. denied sub nom. VSL Corp. v. Conmar Corp., 488 U. S. 1010 (1989); Texas v. Allan Constr. Co., 851 F. 2d 1526, 1533 (CA5 1988); Pinney Dock & Transport Co. v. Penn Central Corp., 838 F. 2d 1445, 1465 (CA6), cert. denied sub nom. Pinney Dock & Transport Co. v. Norfolk & Western R. Co., 488 U. S. 880 (1988); New York v. Hendrickson Bros., Inc., 840 F. 2d 1065, 1083 (CA2), cert. denied, 488 U. S. 848 (1988); Berkson v. Del Monte Corp., 743 F.2d 53, 56 (CA1 1984), cert. denied, 470 U. S. 1056 (1985); Charlotte Telecasters, Inc. v. Jefferson-Pilot Corp., 546 F. 2d 570, 574 (CA4 1976). Second, those courts that do not require "reasonable diligence" have said that the "fraudulent concealment" doctrine seeks to punish defendants for affirmative, discrete acts of concealment; the behavior of plaintiffs is consequently irrelevant. See Wolin, supra, at 852; Robertson v. Seidman & Seidman, 609 F. 2d 583, 593 (CA2 1979); cf. Urland, supra, at 1280-1281 (Becker, J., dissenting). Whether or not that is so in the legal contexts at issue in those cases (which were not antitrust cases), it is not so in respect either to antitrust or to civil RICO. Rather, in both of those latter contexts private civil actions seek not only to compensate victims but also to encourage those victims themselves diligently to investigate and thereby to uncover unlawful activity. See Malley-Duff, 483 U. S., at 151. That being so, we cannot say that the "fraudulent concealment" is concerned only with the behavior of defendants. For that reason, and in light of the Opinion of SCALIA, J. consensus of authority, we conclude that "fraudulent concealment" in the context of civil RICO embodies a "due diligence" requirement. In their brief on the merits, petitioners have asked us to examine whether the Eighth Circuit properly applied the "due diligence" requirement to the evidentiary materials before it. That fact-based question, however, is beyond the scope of our writ; and for reasons similar to those discussed earlier, see supra, at 193, we shall not consider it. The judgment of the Court of Appeals is Affirmed. JUSTICE SCALIA, with whom JUSTICE THOMAS joins, concurring in part and concurring in the judgment. Twice this Term we have received full briefing and heard oral argument on the question of when a civil Racketeer Influenced and Corrupt Organizations Act (RICO) cause of action accrues; when we rise for our summer recess, the question will remain unanswered. We did not reach it in Grimmett v. Brown, 519 U. S. 233 (1997), because we dismissed the writ of certiorari as improvidently granted. And we do not reach it today for no particular reason except timidity-declining to say what the correct accrual rule is, but merely rejecting the only one of the four candidates 1 under which these petitioners could recover. We thus leave reduced but unresolved the well-known split in authority that prompted us to take this case. There will remain in effect, in some Circuits, one of the three remaining accrual rulesthe one that their Courts of Appeals or District Courts have adopted; in the remaining Circuits litigants will have to 1 The Court's opinion could be read to suggest that there are only three different possible accrual rules-last predicate act, injury discovery, and injury and pattern discovery. See ante, at 185-186, 191-193. In fact, as is alluded to in its rejection of the Third Circuit's last predicate act rule, see ante, at 188-189, there is a fourth accrual rule-the Clayton Act “injury" rule. Opinion of SCALIA, J. guess which of the three to follow; and in all of the Circuits no one will know for sure which rule is right—until, at some future date, we receive briefing and argument a third or fourth time, and finally summon up the courage to "unravel," as one commentator has put it, "the mess that characterizes civil RICO accrual decisions," Abrams, Crime Legislation and the Public Interest: Lessons from Civil RICO, 50 SMU L. Rev. 33, 70 (1996). Worse still, the reason the Court gives for regarding the accrual issue as too complex ("subtle and difficult," ante, at 192) to be decided on only the second try is a reason that implicates the merits, and that in my view gets the merits wrong. One cannot, the Court says, leap impetuously to the conclusion that the antitrust "injury" accrual rule applies, rather than a "discovery" accrual rule, because civil RICO cases are unlike antitrust cases, in that "a high percentage" of them "involve fraud claims." Ante, at 191. This erases, it seems to me, the one clear path back out of the current forest of confusion, which is the proposition that RICO is similar to the Clayton Act. This is the proposition that caused us to adopt the Clayton Act statute of limitations in the first place, specifically rejecting the argument the Court now finds plausible, that the preponderance of fraud claims under RICO makes the Clayton Act an inappropriate model. We said the similarity was close enough: "Although the large majority of civil RICO complaints use [fraud] as the required predicate offenses, a not insignificant number of complaints allege criminal activity of a type generally associated with professional criminals such as arson, bribery, theft and political corruption." Agency Holding Corp. v. Malley-Duff & Associates, Inc., 483 U. S. 143, 149 (1987) (rejecting for this reason the use of state-law fraud statutes of limitations). Elsewhere in today's opinion, curiously enough, the Court is quite willing to say that what is good for antitrust is good for RICO-even with respect to a matter much more intimately connected with fraud than the accrual rule, namely, whether |