Since 1987, we have evaluated carboplatin alone or in combination with etoposide in two separate phase II trials of patients with non-small cell lung cancer (NSCLC) who had not received prior chemotherapy. Single-agent carboplatin produced a 20% response rate in 51 patients treated with 390 mg/m2 intravenously every 4 weeks. A 3-day schedule of etoposide 140 mg/m2 on days 2, 3, and 4, and carboplatin 150 mg/m2 on days 1 and 5 also resulted in a 26.7% response rate in 46 patients. Myelosuppressive toxicity associated with carboplatin/etoposide was substantially greater than that seen with carboplatin alone. Carboplatin as a single agent is active in previously untreated patients with advanced NSCLC. The two-drug combination of carboplatin and etoposide also shows activity in NSCLC similar to other combination chemotherapeutic regimens based on comparable prognostic factors in untreated patients. Further evaluation of carboplatin as part of combination chemotherapy in NSCLC is warranted.