To assess the accuracy of preoperative vulva biopsy and the outcome of surgery in vulvar intraepithelial neoplasia (VIN) 2 and 3. In this study 186 consecutive patients with VIN 2 and 3, who were treated with local wide excision or skinning vulvectomy at the Department of Obstetrics and Gynecology, Medical University of Vienna, between 1996 and 2008, were enrolled. Accuracy of preoperative vulva biopsy was assessed by evaluating the rates of correct diagnosis, underdiagnosis, and occult cancer. Histologic findings of preoperative vulva biopsy and surgery were compared. To assess risk factors for incomplete resection, univariate and multivariate analyses were performed, by using the presence of multifocal VIN, histologic grade, patients' age, surgeons' expertise, and lesion diameter as independent variables. VIN 2 and 3 were correctly diagnosed by preoperative vulva biopsy in 55.8% (29/52) and 88.1% (118/134) patients, respectively. Underdiagnosis occurred in 44.2% (23/52) and 11.9% (16/134) of preoperative vulva biopsies with an occult cancer rate of 3.8% (2/52) and 11.9% (16/134) for VIN 2 and 3, respectively. Complete resection was achieved in 43.0% (80/186) of patients. Presence of multifocal VIN was the only factor that was associated with incomplete resection in our study population in univariate and multivariate analyses (P=0.001, P=0.001). Mean patients' age at the time of diagnosis was 51.1 (SD: 15.7) years, multifocal lesions were present in 36.0% (67/186), and the median lesion diameter was 15.0 mm (interquartile range: 10.0-30.0). A significant number of VIN 2 and 3 were underdiagnosed by preoperative vulva biopsy. The rate of incomplete resection after surgery is notable.