The plaintiff filed a bill for injunctive and declaratory relief against the Commissioner (Commissioner) of the Department of Public Welfare (Department) on behalf of herself and her children and on behalf of certain other persons who received public assistance in the form of aid to families with dependent children (AFDC).
The plaintiff alleged the following facts. She did not receive her bimonthly assistance check on or about March 31, 1973, and properly gave notice of that fact to a representative of the Department. The Department has a regulation concerning lost or stolen checks (State Letter 272) which provides in part that “every effort is to be made to avoid delays in order that the replacement check will be received by the recipient on the fourth day after the original mailing date.” Additionally, the Social Security Act (42 U. S. C. § 601 [1970] et seq.) and Federal regulations require that the Department promptly replace assistance checks when it learns that they have not been received. The plaintiff unsuccessfully attempted to obtain a replacement check; the Department generally delays in furnishing replacement checks; and *295the receipt of such a check is of considerable importance to the plaintiff and her children. The plaintiff alleged that this proceeding was appropriately brought on behalf of other recipients of AFDC “who have failed or will have failed during the pendency of this action to receive an assistance check issued by the . . . [Department] and who have or will have been denied a prompt replacement of the check by the Department.”
The bill, filed on April 9, 1973, sought (a) an injunction ordering replacement of all reportedly unreceived AFDC checks “within four days of the mailing of the original assistance checks” and (b) a declaration that (i) the Social Security Act and certain Federal regulations require immediate replacement of public assistance checks and (ii) State Letter 272 requires the Commissioner to replace reportedly unreceived AFDC checks within four days of the mailing of the original check.
The defendant filed a plea in abatement which was sustained. The plea set forth three grounds: (1) the case was moot because the plaintiff had received her replacement check; (2) there was no actual controversy justifying declaratory relief under G. L. c. 231 A; and (3) there was no factual basis presenting a common controversy justifying certification of the class. The Superior Court judge heard the plea on the arguments of counsel and sustained the plea on the ground of mootness. 1 The other two grounds were not considered by the judge and, therefore, no evidence with respect to them was received.
The plaintiff appealed from a final decree dismissing the bill. The Appeals Court did not discuss the mootness question but, with one judge dissenting, affirmed the final decree with a minor modification.2 Wolf v. *296Commissioner of Pub. Welfare, 2 Mass. App. Ct. 812 (1974). The Appeals Court rested its decision on the plaintiff’s failure (1) to allege an “actual controversy”; (2) “to suggest how a grant of the declaratory relief prayed for would ‘remove an uncertainty’ within the meaning of G. L. c. 231 A, § 2”; and (3) to include an allegation which would require the court to grant injunctive relief against a public officer. We granted the plaintiff’s request for further appellate review.3
The reasons advanced by the Appeals Court do not justify the dismissal of the bill.
(1) The existence of an actual controversy never was litigated in the Superior Court. We do not know the Department’s position in response to the allegations that it disregarded State and Federal requirements for prompt replacement of assistance checks.4 Even if the Commissioner admits the plaintiff’s allegations, a dispute may remain over whether the Commissioner properly may continue to disregard his own regulations or Federal requirements, or both. See Woods v. Newton, 349 Mass. 373, 378-379 (1965). This issue cannot be resolved on the defendant’s unsupported allegation that there is no actual controversy when the plaintiff has made factual allegations indicáting that a controversy of some sort is inevitable.5
(2) The Appeals Court’s conclusion that the bill did not suggest how declaratory relief would “remove an uncer*297tainty” (see G. L. c. 231 A, § 2) is not an adequate ground to dismiss the bill. The plea in abatement assigned no such ground. If a court refuses to grant declaratory relief because it would not “terminate the uncertainty,” the reasons for that refusal must appear in the record. G. L. c. 231A, § 3. The allegations of the bill do not show that a declaratory decree would not remove or terminate an uncertainty or controversy. Thus the bill should not have been dismissed on this ground. See Ciszewski v. Industrial Acc. Bd., ante, 135, 139 (1975).
(3) Likewise, the bill should not have been dismissed for failing to show that an injunction was required against a public official. This ground also was not raised by the plea in abatement. In any event, even if the appropriateness of injunctive relief against a public official was not made out in the pleadings, the facts established at trial might justify such an order and declaratory relief might still be appropriate.
We come, then, to the question whether this bill should have been dismissed as moot, as the Commissioner alleged and the Superior Court held. This issue has been the subject of considerable attention in the Federal courts, which have held generally that a class action is not mooted by the settlement or termination of the named plaintiffs individual claim.6
Policies underlying the doctrine of mootness do not require the dismissal of this bill. Rather, they indicate that the judge should have passed on the existence of a proper class before considering the question of mootness. See Sosna v. Iowa, 419 U. S. 393, 399 (1975); Quevedo *298v. Collins, 414 F. 2d 796 (5th Cir. 1969). During the interim between the plaintiffs assertion that she brought the suit in a representative capacity and the court’s certification or refusal to certify the class, the judge should have treated the suit as a class suit for the purposes of dismissal or compromise. Gaddis v. Wyman, 304 F. Supp. 713, 715 (S. D. N. Y. 1969), affd. sub nom. Wyman v. Bowens, 397 U. S. 49 (1970). Gatling v. Butler, 52 F. R. D. 389, 395 (D. Conn. 1971). Washington v. Wyman, 54 F. R. D. 266, 271 (S. D. N. Y. 1971).
Courts decline to hear moot cases because (a) only factually concrete disputes are capable of resolution through the adversary process, (b) it is feared that the parties will not adequately represent positions in which they no longer have a personal stake, (c) the adjudication of hypothetical disputes would encroach on the legislative domain, and (d) judicial economy requires that insubstantial controversies not be litigated. These concerns would have been met here if an actual controversy existed between the plaintiff class and the Department, if the case were appropriate for class treatment and if the plaintiff were an adequate representative of the class. See Spear v. H. V. Greene Co. 246 Mass. 259, 266-267 (1923). See now Mass. R. Civ. P. 23, 365 Mass. 767 (1974).
Several independent considerations militate against holding this case moot. This is a case of asserted importance, “capable of repetition, yet evading review,”7 because the claim of any named plaintiff is likely to be mooted by the mere passage of time during the appeal process. See Dunn v. Blumstein, 405 U. S. 330, 333, *299fn. 2 (1972); Roe v. Wade, 410 U. S. 113, 125 (1973), reh. den. 410 U. S. 959 (1973); Sosna v. Iowa, 419 U. S. 393, 400-402 (1975). In such a case, a court should take particular care that judicial review not be foreclosed on the basis of technical “mootness.” If the underlying controversy continues, a court will not allow a defendant’s voluntary cessation of his allegedly wrongful conduct with respect to named plaintiffs to moot the case for the entire plaintiff class.8 United States v. W. T. Grant Co. 345 U. S. 629, 632 (1953). United States v. Concentrated Phosphate Export Assn. Inc. 393 U. S. 199, 203 (1968). Anderson v. Albany, 321 F. 2d 649, 657 (5th Cir. 1963). Cypress v. Newport News Gen. & Nonsectarian Hosp. Assn. Inc. 375 F. 2d 648, 658 (4th Cir. 1967). Vaughan v. Bower, 313 F. Supp. 37, 40 (D. Ariz. 1970, affd. 400 U. S. 884 (1970). Smith v. Young Men’s Christian Assn. of Montgomery, Inc. 316 F. Supp. 899, 903 (M. D. Ala. 1970), modified on other grounds 462 F. 2d 634 (5th Cir. 1972). Rakes v. Coleman, 318 F. Supp. 181, 191 (E. D. Va. 1970). Crow v. California Dept. of Human Resources, 325 F. Supp. 1314, 1316 (N. D. Cal. 1970), revd. on other grounds 490 F. 2d 580 (9th Cir. 1973), cert, before judgment den. 408 U. S. 924 (1972). Cantrell v. Folsom, 332 F. Supp. 767 (M. D. Fla. 1971). In fact, to establish mootness in such circumstances, a defendant bears a heavy burden of showing that there is no reasonable expectation that the wrong will be repeated; and a defendant’s mere assurances on this point may well not be sufficient.9 United States v. W. T. Grant Co., supra, at 633. United States v. Concentrated Phosphate Export Assn. Inc., supra. Lankford v. Gelston, 364 F. 2d 197, 203 (4th Cir. 1966). Pullum v. *300Greene, 396 F. 2d 251, 256 (5th Cir. 1968). Thus, even after the named plaintiff’s individual claim is satisfied and technically she no longer is a member of the class, she properly might continue to represent the class in vindicating the asserted, rights. Sosna v. Iowa, supra. Rivera v. Freeman, 469 F. 2d 1159, 1163 (9th Cir. 1972). Moss v. Lane Co. Inc. 471 F. 2d 853, 855 (4th Cir. 1973). Conover v. Montemuro, 477 F. 2d 1073, 1082 (3d Cir. 1972). Roberts v. Union Co. 487 F. 2d 387, 389 (6th Cir. 1973). Stokes v. Bonin, 366 F. Supp. 485, 488 (E. D. La. 1973). Davis v. Caldwell, 53 F. R. D. 373, 376 (N. D. Ga. 1971). Thomas v. Clarke, 54 F. R. D. 245, 252 (D. Minn. 1971).
In light of these considerations, we hold that this case should not have been dismissed for mootness. The interlocutory decree sustaining the plea in abatement is reversed; the decree dismissing the bill is reversed; and the case is remanded to the Superior Court for proceedings consistent with this opinion.
So ordered.