College students are engaging in high rates of behavior related to risk of infection from Human Immunodeficiency Virus (HIV) and other sexually transmitted diseases (STDs). A cognitive-behavioral skills training program for heterosexual college females focused on sexual assertiveness skills and the reduction of risk-related behaviors was designed and evaluated and compared to an education-only program. Forty-three heterosexual female undergraduates completed pre-intervention, post-intervention, and follow-up assessments of: 1) HIV/STD-related knowledge, beliefs, and social norms, 2) sexual, alcohol, and drug-related behaviors (self-reports and monitoring), and 3) sexual assertiveness role-plays (videotaped). The participants were randomly assigned to the education-only group (control) and the education-plus skills training group (experimental). The focus of the skills training was on rehearsal of positive behavioral, cognitive, and social alternatives to risk-related behaviors with an emphasis on specific coping strategies. Analysis of covariance on posttest and follow-up scores, using pretest scores as covariates, showed that skills training participants compared to education only participants scored higher on sexual assertiveness skills, specific knowledge of HIV infection, and self-efficacy to perform lower risk sexual behaviors. Skills training compared to education-only participants also reported less frequency of drug use and unprotected oral sex. Self-efficacy and HIV infection knowledge score differences between groups were maintained at 1- month follow-up, although the lower reported frequency of high risk behaviors was not maintained. However, at follow-up consumption of four or more alcoholic beverages on one occasion was reported as less by the skills training participants and the overall reported frequency of high risk behaviors also was reported as approaching significantly less at follow-up by skills training participants. Effective and ineffective aspects of this program as well as the key issue of personal vulnerability and other barriers and facilitators of behavior change are discussed. / Ph. D.