Sinusitis is increased in patients with human immunodeficiency virus (HIV) infection. To determine the underlying mechanism(s), 37 HIV-positive patients were evaluated. HIV-negative controls included 21 with rhinosinusitis, 32 with atopy, and 16 without sinusitis. Twenty-two HIV-positive patients (59%) had sinusitis; 14 of them had AIDS. There was a significant association between sinusitis severity and stage of HIV infection (P < .05). IgE levels were higher in the HIV-positive patients, increased with disease progression, and were strongly correlated with sinusitis severity (P < .01). Of HIV-positive patients, 72% exhibited more than two positive skin tests compared with 24% of HIV-negative rhinosinusitis patients and 12.5% of controls (P < .05). Sinusitis is common in HIV-positive patients, especially those with AIDS. HIV causes an allergic diathesis with increased IgE levels and allergic reactivity. There is a significant correlation between IgE levels and sinusitis severity, suggesting sinusitis is part of this acquired atopic state.