This study evaluates the safety and immunogenicity of the Chiron vaccine HIV p24/MF59. In Part A, 15 volunteers are randomly assigned to receive either HIV p24/MF59 or a placebo at 0, 1, and 6 months. 10 volunteers receive the vaccine and 5 volunteers receive the placebo. If no serious adverse events are observed within 1 week after the first injection in these first 15 patients, Part B is initiated. In Part B, 25 volunteers are randomly assigned to receive HIV p24/MF59 or a placebo at 0, 1, and 6 months. 20 volunteers receive the vaccine and 5 volunteers receive the placebo.