This analysis of how college affects students is based on the largest nationwide study of student development ever undertaken, a ten-year effort by the Cooperative Institutional Research Program of the American Council on Education and the University of California at Los Angeles. Using longitudinal data from over 200,000 students and 300 institutions and employing measures for more than 80 student outcomes, the study covers student attitudes, self-concepts, values, aspirations, behavior patterns, persistence, achievement, competency, career development, and satisfaction. It is shown how outcomes are affected by contrasting types of colleges, and the relative impact is estimated of institutions versus the effects of developing maturity. Examined are policy implications of the study in light of current trends in higher education. It is shown, for example, that the benefits of attending college are being seriously curtailed by recent changes in higher education, including expansion of