Elevated serum concentrations of IgE antibodies to environmental antigens in HIV-seropositive male homosexuals. Forty-five homosexual male subjects with human immunodeficiency virus (HIV) infection, who received care during a 4-month period in an ambulatory center for acquired immunodeficiency syndrome (AIDS), were classified according to their principal presentation with characteristic secondary infections (CDC group IV C, N = 28), cancers (IV D, N = 10), or limited or no symptoms (groups II, III, IV A, or IV B, N = 7). The incidence of allergic rhinitis and conjunctivitis increased after HIV seroconversion by approximately twofold in patients of groups IV C and IV D. The mean serum concentration of IgE was significantly higher for group IV C than for the other HIV-seropositive groups and for a control group of 45 HIV-seronegative homosexual male subjects from the same community who were studied concurrently. More patients in groups IV C and IV D had positive RASTs for a panel of environmental antigens than patients in the other HIV-seropositive groups and the HIV-seronegative control group. Patients with AIDS presenting with typical secondary infections thus have a high frequency of some clinical and laboratory manifestations of allergic diseases. 