In order to evaluate the prognostic significance of fatty acid synthase (FAS), the key enzyme in fatty acid biosynthesis, in ovarian benign and malignant tumors 98 patients with ovarian masses were immunohistochemically evaluated. Histologic features of the lesions and expression for FAS were statistically associated with clinical data and disease-free survival over a 5-year follow-up period. The mean age of patients was 65 years. TNM surgical stages were I in 31.8%, II in 28.2% and III in 40% of cases. The 5-year disease-free survival of the 85 malignant common epithelial ovarian tumors was 47.1% while 35.3 of patients died with active disease. Seventy-eight (79.6%) out of 98 cases expressed FAS in the neoplastic epithelial cells and 42 (42.9%) in the non-neoplastic stromal cells. Statistical analysis revealed FAS expression and stage of the disease to be significantly correlated to recurrence and survival rates only in the malignant common epithelial tumors. Moreover, multivariate analysis showed FAS expression (p=0.05) and tumor stage (p=0.03) to be independent prognostic predictors. FAS is a reliable predictor of recurrence and disease-free survival in common epithelial ovarian tumors along with neoplastic stage. Clinical data, other histologic subtypes and grading were not statistically significant.