The aim of this study was to examine the correlation between cofilin 1 expression and differentiation of epithelial ovarian cancer in patients. We immunohistochemically analyzed 30 patients with primary ovarian epithelial carcinomas, 14 patients with borderline epithelial ovarian tumors, 13 patients with benign epithelial ovarian tumors and 10 normal ovarian tissues. All ovarian cancer patients received the standard therapy, including staging laparotomy and adjuvant chemotherapy consisting of carboplatin and paclitaxel. Cofilin 1 expression gradually increased in normal ovarian tissues, benign tumors, borderline tumors and carcinomas, respectively, and there were significant differences among them (r= 0.94, P<0.05). This suggests a positive correlation between the expression of cofilin 1 and tumor differentiation (r= 0.97, P<0.05). The expression of cofilin 1 may predict the development of ovarian cancer and may be involved in the progression of patients with ovarian carcinoma.