Participants will be enrolled into the study in one of four groups. Each of the four groups will receive 3 mg of the HIV-MAG vaccine alone or combined with one of three different doses of the IL-12 pDNA adjuvant, followed by the VSV HIV gag vaccine boost. Within each of the four groups, participants will be randomly assigned to receive the study vaccines or placebo. At study entry (Day 0), all participants will undergo a physical examination and blood collection. Female participants will also take a pregnancy test. Participants will complete questionnaires and receive counseling on HIV risk reduction. They will also receive their first vaccination. Participants will remain in the clinic for 30 minutes after the vaccination for observation and monitoring.