Recently, sinusitis has been recognized as a frequent clinical problem in human immunodeficiency virus (HIV-1)-infected individuals. We hypothesized that quantitative defects in immune cells in the nasal mucosa of HIV-positive subjects might mirror those in the peripheral blood and explain a predisposition to sinus disease in this population. Nasal mucosa biopsies were obtained from three different groups of patients-HIV-1 seropositive with sinusitis, HIV-1 seronegative with sinusitis, and HIV-1 seronegative without sinusitis (normal volunteer)-and phenotyped for cluster of differentiation antigen (CD) markers. In this study, we found patients with HIV-1 and sinus disease to have significantly lower numbers of both CD3 and CD4 nasal mucosa lymphocytes than seronegative controls in the nasal mucosa (P < 0.05, P < 0.01, respectively). A correlation between nasal mucosal CD4 cells and peripheral-blood CD4 cells was noted (R = 0.67, P < or = 0.01). No deficiency in the number of nasal mucosa T or TC type mast cells was noted for the HIV-1-positive sinusitis group. Further study is warranted to define more completely the pathophysiology and microbiology of, and therapy for, this important clinical problem.