A long-standing line of inquiry in legislative research has dealt with the social backgrounds, recruitment, and career experiences of legislators. This review essay begins by considering the ways in which opportunities to serve in a legislative assembly are distributed in a variety of societies. It then reviews studies of the motives, incentives, and goals of persons seeking legislative offices, and assesses the relationship between the opportunity to serve as a legislator and the desire to do so. Next it considers the processes through which people become members of legislative assemblies, especially contrasting the United States with non-American systems. Finally, the essay takes stock of research on the careers of legislators, and notes findings on the professionalization of the legislative career. Who belongs to legislative assemblies and how they got there are questions which have attracted the attention of a wide variety of scholars. Researchers interested in political elites, in social stratification, in the political role of personality, in the processes of modernization, and many other large matters have studied the backgrounds and careers of legislators. And next to college sophomores, legislators may be the most accessible subjects for social science research around. The result is a large amount of research which seems, on its face, to have little to say to students of legislative institutions. (For review of this general literature, see Lasswell, Lerner, and Rothwell, 1952; Matthews, 1954a; Bell, Hill, and Wright, 1961; Keller, 1963; Marvick,