A cross-sectional correlational design was used to investigate (a) self-efficacy and risk behaviors related to HIV; (b) the comparative predictiveness of self-efficacy and knowledge, attitudes, and beliefs regarding sexual activity and substance use; and (c) possible risk profiles for HIV among adolescents. High school students (N = 427), ranging in age from 12 to 20 years and attending Family Life Education classes in Alameda, California, volunteered to complete a self-administered questionnaire, resulting in a 73% response rate. Ethnic representation included African American, Chinese, Filipino, other Asian/Pacific Islander, Latino, and European American. Over half of this sample of teens were sexually active by the age of 14, with sexually active teens and substance-using teens scoring higher on HIV knowledge, attitudes, and beliefs regarding HIV-related behaviors. Ethnicity consistently appeared more significant in predicting these risk behaviors than gender, self-efficacy, and knowledge, attitudes, and beliefs. The predominance of ethnicity as the predictor for these HIV risk behaviors indicates that theoretical models for behavior change must include a dimension of culture, diversity, and ethnic identity.