The efficacy and toxicity of a combination of carboplatin and cyclophosphamide (CC) were studied in a group of 76 patients with advanced ovarian cancer. Progression-free (PFS) and overall survival (OS) were compared with a historical group of 68 patients treated with cyclophosphamide, adriamycin and cisplatin (CAP-5). Subjective toxicity was compared by measurement of TWIST, the Time Without Symptoms of Treatment or Disease. Of 75 evaluable patients treated with CC, 18 (24%) had a pathologically complete remission (pCR), and 31 (41%) a partial remission (PR). CC led to grade 3 leukopenia in 38% and grade 4 in 3% of 421 treatment cycles. Thrombocytopenia grade 3 was seen after 7% and grade 4 after 2% of cycles. Treatment delay occurred in 11.5% and dose reduction in 21% of cycles. Nephro- or neurotoxicity did not occur. After a median followup of 18 months, the median PFS was greater than or equal to 22 and the OS was greater than or equal to 25 months. Median duration of TWIST was greater than or equal to 22 versus greater than or equal to 10 months after CAP-5 (p less than 0.01). Compared with historical controls, treatment with CC is equivalent to CAP-5. It is free of nephro- and neurotoxicity, but is more myelosuppressive. Quality of life, measured by TWIST, is significantly better during CC. Owing to its equivalent efficacy with lower subjective toxicity, carboplatin should replace cisplatin in treating patients with advanced ovarian cancer.