The introduction offers a ‘global’ survey of the history of communism not only in the geographical sense but also in the sense of seeking to integrate history from above and history from below, social and cultural with political and economic history. The first half offers a synoptic view of the history of communist revolutions before and after 1945, highlighting the tensions between ‘intentionalist’ interpretations that stress human agency and political will and structuralist interpretations that stress the role of impersonal forces. It traces the way in which the meaning of the Russian Revolution was revised in the 1920s from being a mass revolution involving soviet power and radical equality to one concerned with the state mobilization of the human and material resources of a backward society to bring about economic, social, and military modernization. The second half looks at a number of major issues relating to the political, economic, and social history of communism in power. In respect of politics, these include the role of ideology in politics, the relationship of informal to formal political practices, the relationship of ‘neo-traditional’ to modern political practices, and the problem of bureaucracy. In respect of the economy, they include the relationship of the planned economy to the ‘second economy’, difficulties of economic reform, and the shift towards meeting the needs of the consumer from the 1950s. In respect of social aspects, the essay stresses the importance of non-state-directed social processes in shaping the development of communist societies, the reconstitution of forms of social inequality, ideas of cultural revolution, and policy towards women and national minorities. While not attempting to summarize historiography, the introduction seeks to give readers a sense of issues currently under debate.