The mean counts of Langerhans' cells were evaluated in cervical biopsies obtained from 30 patients with human immunodeficiency virus (HIV) infection and cervical intraepithelial neoplasia (CIN) and from 30 HIV-seronegative control patients. Each HIV-seronegative control was matched to a seropositive case with respect to grade of CIN, age, and smoking habits. Langerhans' cells were identified by immunohistochemical staining for S-100 protein. In situ hybridization with biotinylated probes was performed to detect human papillomavirus (HPV) DNA 6/11, 16/18, and 31/35/51. The mean counts of S-100 positive cells per 100 basal cells were lower in HIV-seropositive patients than in controls (0.99 +/- 0.08 vs 1.9 +/- 0.2 P = 0.024). These differences occurred independent of any coexisting HPV infection. Positive correlations between S-100 positive cell counts and CD4+ and CD8+ cell counts were found in HIV-infected women. AIDS patients had lower Langerhans' cell counts compared both to patients with AIDS-related complex or asymptomatic HIV infection. Our results suggest that local cervical immunity, as evaluated by Langerhans' cell counts, is impaired in HIV-seropositive women. The severity of impairment seems to correlate with the stage of the HIV disease.