OBJECTIVES: Using a Life Course Health Development framework, this article summarizes what is known about the impact of cancer and its treatment on the biopsychosocial world of the adolescent and young adult. DATA SOURCES: Published peer reviewed literature, web-based resources, and cancer-related professional organizations' resources. CONCLUSION: Adolescents and young adults with cancer, between 15 and 29 years of age, have emerged as a distinct group requiring specialized care. The demands of cancer and its treatment are often directly counter to the developmental needs of this age group and often alter those life course experiences that contribute to resilience, thriving, and flourishing. IMPLICATIONS FOR NURSING PRACTICE: Providing high-quality care to this age group requires a depth of understanding of the complexity of factors that merge to influence the developmental life course.