Sixty-nine patients having had pretreatment biopsy diagnosis of vulvar intraepithelial neoplasia were treated with surgical excision of all visible lesions. Complete surgical specimens were submitted for pathological study in an attempt to identify occult invasive vulvar carcinoma. Unsuspected invasion was noted in 13 patients (18.8%). Superficial invasion (less than 1 mm) was seen in 8 patients, 4 had greater than 1 mm of invasion, and one verrucous carcinoma was identified. Patients of advancing age with disease that had a raised and irregular surface pattern were more likely to have lesions with occult invasion. Treatment that utilizes ablative techniques cannot be recommended based on the use of preoperative representative biopsies.