The purpose of this study is to identify individual-level characteristics of foster care adolescents who are more likely to not participate in, and drop out of, a life-skills HIV prevention program delivered over 8 months. Structured interviews were conducted with 320 foster care adolescents (15-18 years). Logistic regression and survival analyses (Cox Proportional Hazards Regression) determined the influence of demographics, HIV sexual risk behaviors, substance use, mental health problems, and other individual-level risk factors on nonparticipation and dropout. Older age and having vaginal intercourse without a condom were significant predictors of nonparticipation. Older age and marijuana use significantly increased the hazard of dropping out of the program. Foster care adolescents at increased risk for HIV infection were more likely to never participate in and drop out of the program. To improve initial and ongoing participation, HIV prevention efforts for adolescents in foster care should be tailored to individual-level HIV risk behaviors and incorporate early and ongoing engagement and retention strategies.