The research we report here has had as its aim a study of the acquisition of political philosophy during the adolescent years. We have always known, in a rough and general way, that adolescence is marked by a rapid growth in the comprehension of political ideas. At the threshold of adolescence, at eleven or twelve, the youngster has only a dim, diffuse, and incomplete notion of the political order; by the time he has reached eighteen, he will be, more often than not, a fully formed political creature, possessing a stable and coherent understanding of political structures and functions, and in many cases, committing himself to a philosophy of government. How does this transition take place? In particular, how do learning and cognitive maturation interact to produce these sweeping changes? As a first approach to these questions, we undertook a developmental and cross-national study of adolescents. Youngsters of eleven, thirteen, fifteen, and eighteen were interviewed in three countries: the United States, England, and Germany. (German eleven-year-olds were not interviewed because of fund limitations. Hence, the cross-national analysis compares subjects thirteen through eighteen years of age.) By interviewing youngsters from pubescence to late adolescence we hoped to discern the maturation of political perspectives; by comparing youngsters in three countries with rather different political traditions we hoped to get some sense of the differential impact of social ideas.