This study was performed to identify the contribution of cimetidine to chemotherapy for epithelial ovarian carcinoma. Cimetidine was administered two weeks before surgery in combination with platinum-based chemotherapy, and the treatment was continued for two years. Cyclooxygenase-2 (COX-2) expression was also evaluated. The chemotherapy regimens did not affect patient prognosis. The effect of cimetidine was more marked in patients who showed overexpression of COX-2. Platinum-based chemotherapy combined with cimetidine, as a first-line therapy, may improve the prognosis of patients with advanced serous ovarian carcinoma.