Thirty cases of vulvar intraepithelial neoplasia (VIN) were analyzed in order to determine the frequency of association with human papillomavirus (HPV) infection, and the relationship between this association and patient's age, extent of vulvar lesions, and coexistence with cervicovaginal neoplasia. The presence of condyloma or moderate to marked koilocytosis, now considered as morphological evidence of HPV infection, was observed in 66.6% of our cases. A search for HPV antigens, using the peroxidase-antiperoxidase (PAP) method, was performed in 13 selected cases, and positive staining was detected in 3 of them. The presence of HPV infection correlates with a mean age of 48.8 years, 50% of multicentricity of VIN and coexistence with cervical neoplasia in 30% of the cases, as opposed to a mean age of 55.5 years, 10% of multicentricity of VIN and absence of cervical neoplasia in patients without HPV infection. The demonstration of multiple foci of early stromal invasion in a 43-year-old woman, with multicentric VIN lesions associated with HPV infection, indicates that, even in the presence of such clinicopathological features, the risk of developing stromal invasion should be considered. Considerations are made in relation with the presence of HPV antigen in morphological normal epithelium adjacent to the lesion. Therapeutic implications were also investigated.