The demographic and social relevance of young adult contraceptive use and fertility in developing countries is clear, yet most research attention in this area has been focused on advanced-industrial societies. This doctoral dissertation project will investigate sexual and reproductive transitions among 15-24 year-old women in 21 African and Latin American countries for which Demographic and Health Survey data are currently available. The patterns of sexual activity, contraceptive use, and fertility will be documented, and analyses of their determinants will be performed an an individual micro-level and at a cross-national, multilevel, which will test hypotheses regarding how the micro-level effects are attenuated, magnified, or reversed depending on nation-state and ethnic group contexts. This project will contribute to our understanding of intra- national as well as of cross-national differences in sexual and reproductive transitions. It also will provide an excellent opportunity for a promising young scholar to continue to develop independent research skills.