The increased frequency of cervical dysplasia-neoplasia in women infected with the human immunodeficiency virus is related to the degree of immunosuppression. Cytologic and histologic investigations of the uterine cervix and studies of the lymphocyte functions were performed in human immunodeficiency virus-infected and human immunodeficiency virus antibody-negative women to study possible linkages between human papillomavirus-induced dysplasia and degree of human immunodeficiency virus-induced immunosuppression. Cytologic smears of the uterine cervix of 111 human immunodeficiency virus-infected women were compared with findings in 76 female intravenous drug users negative for human immunodeficiency virus antibodies and in a group of 526 women of the outpatient population of the hospital. Cervical dysplasia-neoplasia (including five cases of invasive carcinoma) was seen in 41% of the human immunodeficiency virus-infected patients. In human immunodeficiency virus-negative intravenous drug users dysplasia-neoplasia was seen in 9%, and in the sample from outpatients in 4%, including two cases of invasive carcinoma (p less than 0.01). Cytologic features that were attributable to infection with human papillomavirus were observed in human immunodeficiency virus-infected women four times more often than in the sample from the outpatient population (p less than 0.01). Frequency and severity of dysplasia appear to increase with diminishing numbers of CD4+ helper/inducer T lymphocytes and correlated significantly (p less than 0.01) with a loss of blastogenic response to phytohemagglutinin, pokeweed mitogen, and tetanus toxoid. These results suggest an increased risk for the development of dysplasia of the uterine cervix in women with human immunodeficiency virus infection, which is related to the degree of immunosuppression. 