Despite radical surgery and aggressive platinum-containing primary chemotherapy, the outcome of patients with advanced ovarian cancer remains extremely poor; most of them suffer from recurrent or progressive disease. These patients should be treated with an effective second-line therapy showing only few toxic side effects so as not to affect quality of life. From July 1992 to August 1996, 88 patients with recurrent or progressive ovarian cancer have been treated with treosulfan, an alkylating agent, in our department. All of them could be evaluated for toxicity and 80 for response. There were 2 complete and 13 partial responses, giving an objective response rate of 19%. Among responding patients, median survival time was 41 months. Thirty-four percent of the patients had stable disease with median survival of 18 months. Thirty-eight (47%) nonresponding patients showed a survival time of only 5 months. In 48 women with progressive disease within 12 months after primary therapy, a response rate of 19% and stable disease in 31% could be achieved. Toxic side effects were rare and moderate in intensity. Life-threatening myelosuppression, emesis resistant to therapy, and alopecia were not observed. It can be concluded that tresosulfan is an effective drug in second-line therapy for patients with recurrent or progressive ovarian cancer without affecting quality of life.