HIV-seronegative volunteers (including four populations at higher risk for HIV infection and two populations at lower risk) receive one of four regimens. Two treatment groups receive 50 mcg SF-2 rgp 120 (BIOCINE) in MF59 adjuvant or 600 mcg MN rgp120 (Genentech) in alum. Two control groups receive vehicle (placebo) in MF59 adjuvant alone or alum adjuvant alone. Immunizations are given at months 0, 1, and 6. AS PER AMENDMENT 10/93: patients enrolled by June 15, 1993, receive a fourth immunization at month 12 or 18 (50 percent of patients for each schedule). Patients are followed until 2 years after the first injection. AS PER AMENDMENT 05/10/94: a special study of vaccine acceptability and HIV-related risk behavior will be conducted at some time between months 12 and 18. AS PER AMENDMENT 07/02/97: a special DTH study will be conducted in consenting volunteers who have received three or four immunizations. The injections will be given at the end of the study (on or after day 1, & 56). Followup is extended to 56 days after administration of the intradermal injection.