Eighty-eight patients with stage IIB-III epithelial ovarian cancer were randomised to receive first line single agent cisplatin (100 mg/m2) monthly or carboplatin (400 mg/m2) monthly for up to 5 cycles. Crossover to the opposite analogue occurred with progression or lack of response. All patients were premedicated with i.v. methylprednisolone (500 mg at 0 hours and 250 mg at 3 hours) and the first 20 patients in both groups received lorazepam and prochloperazine for nausea and vomiting. The median number of vomiting episodes per cycle with cisplatin was 16 and with carboplatin 2 (p less than 0.001). In the cisplatin arm 27/40 (67.5%) developed mild renal toxicity, 9/40 (22.5%) WHO grade I neurotoxicity and 18/40 (45%) evidence of ototoxicity at audiometry. To date we have seen no neuro- or ototoxicity with carboplatin and 1/40 (2.5%) have developed WHO grade I renal toxicity. Myelosuppression and anaemia was more common with carboplatin but only 1 episode of grade IV thrombocytopenia has been seen with first line carboplatin. The clinical response rate (CR+PR) for cisplatin was 19/40 and for carboplatin 27/40. Actuarial survival for cisplatin group at 24 months was 50% and for carboplatin group 58% with no significant difference. Carboplatin appears less toxic than cisplatin producing to date similar survival and response as a single agent.