Data from the National Longitudinal Surveys of Youth 1979 and 1997 cohorts were used to compare welfare use, fertility, educational attainment, and marriage among teenage women in the years before and immediately following welfare reform. The first objective was to document differences between these cohorts in welfare use and outcomes and behavior correlated with entry into welfare and with future economic and social well-being. The second objective was to investigate the causal role of welfare reform in behavioral change. Significant differences were found between cohorts in welfare use and in outcomes related to welfare use. Furthermore, difference-in-differences estimates suggest that welfare reform has been associated with reduced welfare receipt, reduced fertility, and reduced marriage among young women who, because of a disadvantaged family background, are at high risk of welfare receipt. Finally, in the post-welfare reform era, teenage mothers are less likely to receive welfare and are more likely to live with at least one parent than in the pre-reform era. Establishing more definitively that welfare reform is responsible for these changes will require further investigation. © 2003 by the Association for Public Policy Analysis and Management.