Adolescence as a developmental phase contains certain features that can be regarded as universal. It is an eventful time, with opportunities for growth as well as vulnerability and risk. Interwoven with the universal characteristics of adolescence are various constitutional factors and experiences which may influence the adolescent towards either developmental progress or dysfunction. For example, trauma and victimization, as well as social stressors such as poverty and racial discrimination, may place young people at risk. Drawing upon established theories as well as more recent research findings, the chapter presents some ways to understand both normal adolescent development, and adolescent risk, vulnerability, and resilience. Substance abuse frequently accompanies both developmental dysfunction and specific disorders of adolescence. The chapter highlights the relationship between those issues and adolescent substance abuse in an ecosystemic framework. References