Thirty-four previously untreated patients with extensive small cell lung cancer were treated with a combination of carboplatin 300 mg m-2 i.v. on day 1 and etoposide 100 mg m-2 i.v. on days 1, 2 and 3 every 28 days. Thirty-two patients were assessable for response. Eighteen patients (56%) achieved an objective response (95% confidence limits 38%-73%). Five (16%) had a complete response and 13 (41.0%) had a partial response. The median time to response was 7.8 weeks and the median duration of response was 23.1 weeks (range 6.2 to 54 weeks). The median survival of all 34 extensive disease patients was 34.7 weeks (range 1.3-59.3 weeks). Myelosuppression (leukopenia) was the main toxicity. There was one early death that may have been treatment-related. Biochemical renal dysfunction was noted in two patients. Paresthesiae and tinnitus/hearing loss were described by three and two patients respectively. Serious gastrointestinal toxicity was infrequent. This and other studies have shown this combination to be active and well tolerated in small cell lung cancer; however, it is not yet clear if it is as efficacious as the more commonly used VP-16-cisplatin regimen.