Primary: To determine in healthy volunteers whether priming with a vaccinia HIV-1 gp160 envelope gene recombinant vaccine (HIVAC-1e) followed by boosting with one of two subunit recombinant HIV-1 envelope vaccines (Env 2-3 and gp120) provides enhanced immunogenicity compared to vaccination with the gp120 subunit vaccine alone. (Per 10/01/92 amendment, boosts with VaxSyn (gp160) were eliminated.) To evaluate the immunogenicity of one versus two priming doses of HIVAC-1e prior to a boost with gp120. To compare the relative immunogenicity of the three subunit vaccines when administered as boosters.