A total of 34 patients with advanced ovarian cancer, who relapsed 1-72 months after at least one first-line cisplatin-based chemotherapy protocol, were treated with carboplatin, 350 mg/m2 q 4 weeks, with the adjunct of primary prophylactic granulocyte colony stimulating factor (G-CSF; filgrastim), 300 or 480 microg daily, days 5-9. Over 90% of the anticipated dose of carboplatin could be administered. Partial response, defined as a decline in CA-125 of 50% or more on two consecutive samples, occurred in 42%, while 15% of patients achieved a complete response (no clinical signs of disease with normalization of CA-125). Survival from start of carboplatin treatment was 23 months. Myelosuppression was the most important toxicity with 35% of patients experiencing grade 4 thrombocytopenia of short duration. Grade 4 leucopenia occurred in only one patient. It is concluded that single-agent carboplatin, with the adjunct of prophylactic G-CSF, can be administered with adequate dose intensity, and is an effective and acceptable palliative treatment for patients with relapse after first-line cisplatin-based chemotherapy.