This study investigated age changes in risk perception and unrealistic optimism. Teenagers (n = 376) and parents (n = 160) evaluated the risk of experimental, occasional, and regular involvement in 14 health-related activities (e.g., getting drunk). Respondents also evaluated their comparative changes of encountering the leading causes of morbidity and mortality. Compared with adults, teenagers minimized the perceived risk of experimental and occasional involvement in health-threatening activities. Notably, teenagers were less optimistic about avoiding injury and illness than were their parents, and teenagers at greatest risk for such misfortunes were the least optimistic about avoiding them. These findings do not support traditional explanations of adolescent risk taking. The implications of these findings for understanding and preventing health-damaging behavior among adolescents are discussed.