BACKGROUND We evaluated the clinical features, treatment, and survival status of the patients with borderline ovarian tumors. METHODS A retrospective review of the charts of 150 patients with borderline ovarian tumor registered at the Tokai Ovarian Tumor Study Group from January 1, 1980, to December 31, 1994, was conducted to obtain clinical and pathological information. RESULTS In stage II and III disease, the numbers of patients with no residual tumor, residual tumor of <2 cm, 2-5 cm, and >5 cm were 9, 10, 3, and 3, respectively. The sizes of residual tumors and corresponding clinical response to chemotherapy were as follows: residual tumor of <2 cm, complete response (CR), 6 patients; no change (NC), 2; progressive disease (PD), 2; tumors 2-5 cm, NC, 1 patient, PD, 2; tumors >5 cm, PD, 3 patients. The survival for patients with residual tumor <2 cm was significantly better than for those with residual tumor from 2-5 cm and of >5 cm (P < 0.05). The survival for patients with stage II and III serous tumor was significantly longer than that for patients with stage II and III mucinous tumor (P < 0.05). CONCLUSIONS In advanced borderline ovarian tumor, the prognosis of patients with gross residual tumor after initial surgery, and especially with mucinous tumor, was poor.