In this series 49 patients with epithelial ovarian carcinoma previously treated with platinum-based chemotherapy received leucovorin 200 mg/m2 i.v. bolus followed by 5-fluorouracil at 370 mg/m2 i.v. bolus daily for 5 days every 4 weeks for the first two courses and subsequent courses were given every 5 weeks. Of this group, 47 patients were evaluable for toxicity and 44 for response. Of the patients evaluable for response, 15 were considered platinum-sensitive and 29 were platinum-refractory. The overall response rate was 6/44 (13.6%). There were two complete responders (4.5%) and four partial responders (9.1%). In the platinum-sensitive patients, there was one complete response, yielding a response rate of 6.6%, whereas in the platinum-refractory patients, there were four partial responses and one complete response for a response rate of 17.2%. Five responses were in the pelvis and there was one response at an extrapelvic site in the abdominal mesentery. The median number of courses delivered was three (range: 1-10). The major adverse effect was myelosuppression with 16/47 (34.0%) experiencing granulocytopenia < 1,000/mm3. The median white blood count nadir for the patients experiencing any leukopenia was 2,700 (range: 400-3,900/mm3). There was one episode of grade 3 thrombocytopenia. Grade 3 intestinal toxicity was seen in seven patients (14.9%). There were no treatment-related deaths. In this previously treated population, 5-fluorouracil with high-dose leucovorin exhibited activity of interest in the platinum-refractory population and warrants further investigation.