p16, a member of the INK4a family of cyclin-dependent kinase inhibitors, is known as a negative regulator of cell cycle progression and differentiation. Although p16 has been shown to be a promising biomarker for the detection of cervical intraepithelial neoplasia, few data have been published on vulvar cancer. Using immunohistochemistry, we evaluated the expression of p16 in 80 cases of invasive vulvar squamous cell carcinoma. Results were correlated with clinicopathologic parameters and survival data to determine the prognostic significance of p16 in vulvar cancer. p16 expression was detected in 34 of 80 (43%) cases of invasive vulvar squamous cell carcinoma. The expression was localized to the cytoplasm and the nuclei of the tumor cells. Correlations between p16 expression status and any clinicopathologic variables failed to be of statistical significance. In a univariate analysis, groin lymph node status, tumor stage, and tumor grade were associated with disease-free and overall survival, respectively. Patients positive for p16 expression showed a significantly longer disease-free and overall survival by univariate analysis. p16 expression was not associated with survival in a multivariate Cox-regression model. Our data add on those published in the literature and suggest that p16 may be of prognostic significance in invasive vulvar squamous cell carcinoma.