The process of order-to-disorder transition (ODT) has been studied in a symmetric diblock copolymer AB and in an asymmetric miktoarm star block copolymer of the AB(3) type. We find that the T-ODT depends on the ordering temperature just as the melting temperature in semicrystalline homopolymers depends on the crystallization temperature. In this work we show, for the first time, the existence of an equilibrium transition temperature (T-ODT(0)) and we demonstrate how this can be obtained. The dependence of the apparent T＇(ODT) on the supercooling is attributed to grains of different sizes.