The essential purpose of this article is to determine the extent of the CPSU's membership presence in modern Soviet science,1 as part of a larger study of the Party's involvement in science management. Statistics alone cannot determine the state of Party-science relations, but a study of the nature of and changes in Party membership rates and recruitment patterns provide hypotheses to be tested by descriptive analyses of Soviet science politics and policy-making in larger studies. This study begins with a section on the historical development of Party membership among scientists which might seem unconnected with the the rest of the article, but which in fact is of some importance in gaining an understanding of the character of the top scientific leadership of today. Modern Soviet statistics and descriptive data from both Soviet and émigré sources are then used to arrive at measures of Party membership levels in Soviet research institutes among all categories of personnel. A somewhat discriminatory policy in Party recruitment among the intelligentsia in conditions of a rapidly expanding research establishment has produced a rather lower level of Party membership than might have been expected. Nevertheless the Party presence, at all levels, is impressively solid. The concluding section of the article, which examines the incentives and motivations of researchers to join the Party, confirms the enormous significance of even such a limited aspect of the CPSU's involvement in science as simple Party membership.