¶1OPINION OF THE COURT
¶2Memorandum.
¶3The order of the Appellate Division should be affirmed, with costs, for the reasons stated in the opinion of Justice Vincent A. Lupiano in that court (78 AD2d 303). In view of the recognition of the difference in determining when the liability of the insurer attaches under group medical insurance policies between the time of the occurrence of the event insured against and the time of the incurring of the expenses occasioned thereby — which determinations are generally resolved on the basis of the specific language used in the policies (e.g., Ann., 66 ALR3d 1205, 1208-1218; 68 ALR2d 249, 275-283) — the failure of the insurer to make unmistakably explicit provision in this policy as to which shall control creates an ambiguity which under familiar principles of construction is to be resolved against the insurer.
¶4*928Chief Judge Cooke and Judges Jasen, Gabrielli, Jones, Wachtler, Fuchsberg and Meyer concur.
¶5Order affirmed, with costs, in a memorandum.