This is a randomized, double blind study of the safety and immunogenicity of APL 400-003, a plasmid DNA vaccine encoding the env and rev genes of HIV-1, in HIV-negative volunteers. Four doses of vaccine are being tested: 100, 300, 1000, and 3000 micrograms. 8 volunteers per dose will be randomized: 6 to plasmid vaccine, and 2 to a vehicle control. Immunizations will be administered at day 0 and weeks 4 and 8, with a booster immunization administered at week 24. An additional 5 volunteers may be included in an open manner at the dose likely to be used in subsequent studies. The primary aims of the study are to determine: 1. the safety of APL 400-003, as evaluated by clinical and laboratory safety parameters and 2. the immunogenicity of APL 400-003, as determined by a broad range of laboratory assays. Up to 41 patients (allowing for drop-outs) will be enrolled in the study, and volunteers will be followed for one year after immunization.