Twenty homosexual men who reported having sexual contact with homosexual men who had the acquired immunodeficiency syndrome (AIDS) or the AIDS-related complex were examined to determine their clinical status, immunologic profiles, and the presence of antibody to the human T-cell lymphotropic virus type III (HTLV-III). Of the 20, eight men had one or more signs or symptoms of the AIDS-related complex and 12 were asymptomatic. Antibodies to HTLV-III were present in 14 (70%) of 20 of the sexual contacts as compared with four (10%) of 40 healthy homosexuals without known contact with a patient who had AIDS (P less than .0001). Seropositive contacts had significantly higher mean counts of suppressor lymphocytes and lower helper: suppressor ratios (P less than .05 and .005, respectively) and higher serum levels of IgG than seronegative contacts (P less than .05). It was not possible to determine significant differences in sexual practices, drug use, length of relationship, or numbers of different sexual partners between symptomatic and asymptomatic contacts or between seropositive and seronegative contacts in this study.