The opening of archives in recent years makes it possible to reassess the membership of the Communist Party of Great Britain (CPGB) before 1945. The revised aggregate figures, while not startling, suggest that revisions to established views of the effects of the General Strike, the shift to the ‘new line’ and the popular front, are in order. The party's membership was very predominantly male, tended to be young, often included a high proportion of unemployed people, and was heavily working class, with miners especially significant. Geographically, its membership was dominated for most of the period by London, Scotland, Lancashire, and South Wales. There was also a very high turnover of membership for much of the period. The reasons for this turnover, and explanations for the circumstances in which the party was best able to recruit, are discussed. Over time the party's membership did become less unrepresentative of Britain as a whole, enabling it to become an organic, if minor, part of British political life. CPGB membership patterns have similarities with those of other Western Communist parties and its predecessor organizations in Britain, showing how the CPGB reflected features of both international Communism and the British left.