This study examined the trajectories of sexual risk behaviors among adolescents from ages 15 to 23 and factors associated with those trajectories. The sample was 5,419 adolescents from the 1997 National Longitudinal Survey of Youth. Using group-based trajectory modeling, five distinctive trajectory groups were identified. The High group had a high and increased risk trajectory over the observed ages. The Decreased group had a risk trajectory that accelerated before age 19, but decreased afterwards. The risk trajectories of the Increased-Early and Increased-Late groups were low at age 15 but increased significantly starting at ages 16 and 18 for the groups, respectively. Participants in the Low group remained at low risk over time. Sexual risk behaviors were also positively associated with alcohol use, marijuana use, and delinquency. Results highlight the need for intervention efforts to consider developmental timing of sexual risk behaviors and their associations with other problem behaviors. (Contains 2 tables and 2 figures.)