Testicular cancer is the most common solid tumor among males in the 20- to 39-year age range. Moreover, testicular cancer has unique biological associations, clinical features, and psychosocial impacts that establish this tumor as a prototypic malignancy of young adults. The biology of testicular germ cell tumors after puberty is distinctive. Epidemiologic patterns of testicular cancer suggest etiologic factors that may be congenital, racial, and geographic. The clinical management of a cancer common among young adults, but rare among adults in general, requires expertise so as not to jeopardize the high rates of survivorship associated with modern therapy. The concurrent but separate development of staging, prognostic systems, and treatment recommendations between the fields of pediatric and adult oncology highlights the need for increased integration and cooperation across these subspecialties. The high rate of survival, combined with the need for long-term monitoring for relapse or late effects, demonstrates the challenge of delivering longitudinal care in this mobile and active young adult population.