Participants complete a total of 6 scheduled study visits: 2 at baseline, 2 at follow-up 6 months later, and 2 at follow-up 12 months after enrollment. Participant risk behaviors and knowledge of and attitudes toward HIV vaccine and other HIV prevention trials are assessed at each time point. HIV infection status is tested by standard HIV ELISA and Western blot at follow-up, as well as at participant request throughout the study. Participants are instructed to recognize and report suspected primary HIV infection based on symptoms or high-risk exposures. HIV pre-test, risk reduction, and post-test counseling is provided in accordance with CDC standards of practice. Participants who become infected with HIV during the study are counseled and referred for medical and psychosocial services.