The slides of 64 vulvectomy specimens from vulvar squamous carcinoma were reviewed in order to study the histopathologic changes adjacent to the neoplasia. Normal epithelium was found in 7 cases (11%) and epithelial alterations adjacent to carcinoma in 59 (89%). The epithelial alterations found were: nonneoplastic epithelial disorder (NNDV) in 38 cases (59%) and vulvar intraepithelial neoplasia (VIN) in 19 (30%). The distribution of NNDV was: 20 cases of epithelial hyperplasia (EH) (31%), 6 of lichen sclerosus (9%) and 12 of the mixed type (19%). Sixteen cases of VIN 3 (25%) were undifferentiated, and three cases were differentiated VIN. Eighteen of 19 VIN cases were associated with NNDV, and 8 cases of undifferentiated VIN were associated with human papillomavirus infection. There was no apparent relationship between the associated lesions and tumor size, depth of invasion, lymph node metastases and clinical stage. Nevertheless, we found a significantly higher frequency of associated lesions in poorly differentiated tumors (P > .01). The most important finding was a high association between EH (50%) and VIN (30%) with carcinoma. VIN cases were almost always (95%) associated with EH.