Thirty-two patients with carcinoma in situ of the vulva were analyzed with respect to age-specific incidence rates, associated human papilloma virus (koilocytosis and condyloma) changes, and multifocal, unifocal distribution of the lesions. The association of koilocytosis and condyloma changes in the neoplastic epithelium correlated with a younger mean age compared to those without human papilloma virus (HPV) changes (39 versus 67 years). Also, patients with multifocal disease were found to have a younger mean age compared to those with unifocal disease (31 versus 61 years). Carcinoma in situ of the vulva appears to be a disease that affects two patient population groups. Patients with coexistent HPV infection usually are younger and have multifocal disease, and those patients with a variable history of HPV infection usually are older and have unifocal disease.