To investigate the influence of HLA specificities on the rate of progression and outcome of human immunodeficiency virus (HIV) infection, we performed (a) a case-control study in 1989-1990 of HIV-seropositive individuals stratified by both risk behavior and ethnic background, (b) a longitudinal cohort study of HIV-infected male homosexuals enrolled in 1981-1982, and (c) an analysis of individuals with a diffuse infiltrative CD8 lymphocytosis syndrome. In the case-control study, there was a significantly higher frequency of HLA-B35 among intravenous drug users, but not homosexuals, who developed illnesses meeting the case definition for AIDS compared with asymptomatic HIV-positive controls, regardless of ethnic status. In the longitudinal study, HLA-B35-positive homosexuals had a significantly increased rate of progression to AIDS and decreased survival over a 7-year period compared with those without this specificity. Finally, there was a significantly decreased frequency of HLA-B35 in individuals with the diffuse infiltrative lymphocytosis syndrome, a clinically and genetically distinctive disorder occurring in HIV infection in which a low rate of progression to opportunistic infections was found. The high rate of salivary and lacrimal gland lymphoma in this group suggests that there is dissociation between the presence of HLA-B35 and the development of particular AIDS-defining conditions. We conclude that HLA-B35 is a risk factor for more rapid progression to AIDS, particularly opportunistic infections and Kaposi's sarcoma, operating in groups with high rates of newly acquired HIV infections such as New York City male homosexuals in 1981-1982, and intravenous drug users in 1989-1990.(ABSTRACT TRUNCATED AT 250 WORDS)