In a group of 20 immunosuppressed women with lower genital neoplasia, evidence of associated human papillomaviral infection was found in all patients on the basis of the histologic identification of koilocytes in the upper strata of areas of mild or moderate dysplasia. Immunohistochemical study of similar areas disclosed human papilloma structural antigens in the lesions in 60%, while 50% had lesions in which human papilloma virions were detected by the electron microscope. An abnormal immunologic status, indicated by an altered T-helper/T-suppressor ratio, a deficient response to mitogenic stimulation, or both, was confirmed in 80% of the patients studied. Twelve of the 20 patients had unusually persistent and recurrent intraepithelial neoplasia, and in one the disorder progressed to invasive epidermoid carcinoma. The progressive behavior of human papillomavirus-associated neoplasia in these immunosuppressed patients might represent an accelerated version of the long-term course of such lesions in immunocompetent hosts.