In Part A, 32 volunteers (eight on each of four treatment arms) are randomized to receive one of two doses (15 or 50 mcg) of gp120 vaccine with either MTP-PE/MF59 adjuvant emulsion or MF59 emulsion alone. The volunteers receive three IM injections at 0, 1, and 6 months. In Part B, 16 female volunteers (eight on each of two treatment arms) are randomized to receive either MF59 emulsion alone (placebo) or MF59 emulsion plus gp120 vaccine (50 mcg). Volunteers receive five IM injections at monthly intervals.