There are 2 types of vulvar intraepithelial neoplasia (VIN): warty-basaloid and differentiated. Differentiated VIN is uncommon and seldom diagnosed prior to carcinoma and, traditionally, is not graded. There are currently 3 grading systems for warty-basaloid VIN: the World Health Organization (WHO) 3 grade system of VIN 1-3, a 2 grade system of low and high grade vulvar intraepithelial lesions, and the revised International Society for the Study of Vulvovaginal Disease (ISSVD) classification which has no grading of VIN. According to the ISSVD, VIN 1 should be abolished and VIN 2 and 3 combined into a single category, simply termed warty-basaloid VIN. To determine the best system for grading warty-basaloid VIN and learn more about differentiated VIN, we reviewed the pathology of 164 consecutive women with VIN. Of these, 134 (82.3%) had warty-basaloid VIN, 29 (18.2%) had differentiated VIN, and 1 had both. Of warty-basaloid VIN cases, 4 had VIN 1, 13 VIN 2, and 118 VIN 3 when graded according to the WHO. All VIN 1 occurred in condylomata acuminata. VIN 2 and 3 were distinguished only by degree of abnormality. Differentiated VIN was diagnosed before SCC in only 7 cases (26.7%). Because the only VIN 1 cases seen were in condylomata acuminata and because VIN 2 and 3 were difficult to distinguish and there appears little clinical reason to do so, our study supports the ISSVD proposal that VIN 1 be abolished and VIN 2 and 3 be combined. There needs to be more clinical awareness of vulvar conditions, so that differentiated VIN is biopsied before cancer has supervened.