The 1990s saw considerable advances in the state of research on adolescence and youth. This article provides a critical commentary on a subset of this research, focusing on the causes and consequences of the lengthened period in which the transition to adulthood occurs. It provides a brief history of adolescence research, identifying a select set of topics, themes, and research problems that will guide research on adolescence and youth over the next decade. These research foci, which include peer group relations, biological influences on adolescence, employment experiences, increased autonomy, and racial and gender differences, are described as representing either continuities or advances in adolescence research. The strengths and shortcomings of this research are detailed. The paper concludes by suggesting promising areas for future research and by providing guidelines for undertaking such research.