Although approximately one-third of all children born in the United States are expected to spend some time living in a married or cohabiting stepfamily, our understanding of the implications of stepfamilies for the well-being of youth remains incomplete. Using data from the National Longitudinal Study of Adolescent Health, this research investigates adolescent depressive symptomatology and suicide ideation in stepfather families, paying careful attention to variation in pathways of stepfamily formation. I test multiple theoretical explanations for the effects of family structure on adolescent emotional well-being, including perspectives emphasizing economic deprivation, socialization and social control, stress and instability, and community connections. I also explore the possibility that observed associations between family structure and youth well-being might be spuriously produced by the preexisting selective characteristics of stepfamilies. The results of this research point to a complex relationship between stepfamily formation and adolescent emotional well-being, suggesting both positive and negative effects. (Contains 3 tables and 8 notes.)