The collapse of the Soviet Union has made a thoroughgoing reassessment of the theoretical orientations of Sovietology and post-Sovietology indispensable. Without an analysis of what went wrong in standard approaches within the former field of Soviet studies, we are unlikely to build any scholarly consensus about how to analyse the turbulent post-Soviet milieu, This essay argues that one crucial theoretical issue remained unresolved in all major branches of Sovietology: the question of how to define regime identity in conceptual and comparative terms. Specifically, neither the totalitarian model nor modernization theory clearly set out any theoretical criteria that could be used to demarcate the beginning and ending of the “Soviet regime” as a distinct entity. As a result, long before the Soviet Union actually collapsed in 1991, most scholars had already concluded that the “Soviet regime” established in 1917 had ceased to exist, conceptually. Indeed, the same theoretical problem in defining regime identity bedevils current analyses of the “Yeltsin regime,” making the resolution of this issue all the more important.