We disagree with the majority’s conclusion that, “[bjecause petitioner’s retired members do not have any contractual rights with respect to health insurance benefits, they may not challenge the change in benefits.” In our view, Supreme Court properly concluded that the City’s determination to change the health insurance benefits paid to retirees violated the established past practice of providing a certain level of benefits to them.
It is well established that substantive rights may arise not only through collective negotiations, but also through consistently followed past practices (see, Matter of Incorporated Vil. of Hempstead v Public Empl. Relations Bd., 137 AD2d 378, 383, lv denied 72 NY2d 808; Matter of State of New York [Governor’s Off. of Empl. Relations] v New York State Pub. Empl. Relations Bd., 91 AD2d 718). Furthermore, where such a past practice is shown to exist, the employer is not free to discontinue it without prior negotiation (see, Matter of Incorporated Vil. of Hempstead v Public Empl. Relations Bd., supra, at 383; Matter of Board of Coop. Educ. Servs. Sole Supervisory Dist. v New York State Pub. Empl. Relations Bd., *104482 AD2d 691, 693-694). Although Resolution No. 33 did not confer any vested rights to the retirees, that resolution established a practice of providing benefits to all retirees equivalent to the coverage provided to current employees; a practice that respondent, City of Geneva (City), consistently adhered to for 24 years until unilaterally terminating such practice effective January 1, 1997. We agree with the court that the City’s continuous provision of those benefits to the retirees established a past practice that gave rise to a substantive right. The City, as a public employer, had a duty to continue past practices that involve mandatory subjects of negotiation (see, Matter of Unatego Non-Teaching Assn. v New York State Pub. Empl. Relations Bd., 134 AD2d 62, 64, lv denied 71 NY2d 805), which include changes in health insurance programs. (Appeal from Judgment of Supreme Court, Ontario County, Harvey, J.— CPLR art 78.) Present—Green, J. P., Lawton, Callahan, Doerr and Balio, JJ.