Based on their good activity and minimal toxicity in non-small cell lung cancer and other cancers, we initiated a phase II trial of carboplatin plus paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) in the treatment of patients with previously untreated stage IIIB and IV non-small cell lung cancer. Among 51 patients treated, the overall response rate was 27.5% (14 partial responses). Seventeen patients had stable disease, while 16 patients experienced disease progression after two cycles of treatment. Apart from myelosuppression, toxicity has been modest, with fewer than 5% of patients experiencing grade 3 or greater nonhematologic toxicity. Objective response and survival rates were modestly improved among patients given the higher of two paclitaxel doses (175 mg/m2 v 135 mg/m2). These data suggest that paclitaxel plus carboplatin warrants further study in metastatic non-small cell lung cancer.