This study evaluated the impact of psychosocial and knowledge-related antecedent factors on adolescents' sexual, alcohol-use, and drug-use behaviors associated with the transmission of STDs, including HIV. Additionally, the study examined the role of peer influences in determining STD and HIV risk behaviors, relative to knowledge and other psychosocial factors. Researchers surveyed 544 freshmen (9th graders) at 4 urban high schools, collecting the data through anonymous, self-administered questionnaires. The report provides a tabulation of the students' demographic and other characteristics. In order to analyze the data, the researchers employed a multiple regression model. The results of this analysis indicates that higher levels of STD and AIDS knowledge were associated with lower levels of STD and AIDS anxiety, fewer negative attitudes towards people with AIDS, stronger perceptions of self-efficacy in preventing infection, and stronger peer affiliation. Moreover, negative attitudes toward people with AIDS were inversely related to knowledge, social support, and perceived self-efficacy. The study also found that perceived peer norms and strong peer affiliation served as predictors of alcohol and drug use, while lower levels of knowledge and perceived peer norms served as predictors for nonuse of condoms. The findings of this study reveal several factors related to adolescents' risk of acquiring STDs: the connection between peer influence and adolescent risk behaviors, the relationship between the use of alcohol and drugs and sexual risk behavior, and the role of knowledge in determining the specific risk behavior of nonuse of condoms.