The relation between serological and immunologic profiles and the risk of developing AIDS was assessed in 306 initially asymptomatic, human immunodeficiency virus-infected homosexual men studied for 30 mo. Twenty-nine men developed AIDS (attack rate, 16.8%). The attack rate in core antibody-negative men was 35.7%; this rate was 43.9% in antigen-positive men, 51.9% in men with low (less than 0.5 x 10(9)/L) CD4+ cell counts, 6.8% in core antibody-positive men, 6.9% in antigen-negative men, and 6.1% in men with normal CD4+ cell counts. The disappearance of core antibody, the expression of antigen, and the occurrence of low CD4+ cell counts preceded AIDS by a median of 624, 544, and 466 d, respectively. Seronegativity for core antibody preceded AIDS in 21 of 26 patients, 20 of whom were also antigen positive. Four more cases of AIDS developed among the antigen-negative, core antibody-positive men with low CD4+ cell counts. Only one patient with AIDS escaped detection by using these three markers.