Developmental trajectories of risky sexual behavior were identified in a multiethnic sample of 1,121 youth drawn from the Children of the National Longitudinal Survey of Youth data set (NLSY79). Group-based trajectory modeling of a composite index of sexual risk taking revealed four sexual risk groups from ages 16 to 22: low risk, decreasing risk, increasing risk, and high risk. The Low Risk group exhibited low levels of risk across the study period. The Decreasing Risk group had high levels of sexual risk in adolescence that declined in early adulthood. The Increasing Risk and High Risk groups showed distinct risk patterns during adolescence but converged in early adulthood. When compared with adolescents in the low-risk group, individuals in the other groups were more likely to be male, had mothers who had an early birth, were less likely to live with both biological parents in early adolescence, had higher risk proneness, and reported more negative peer pressure. (Contains 6 tables and 1 figure.)