In studies conducted by the Eastern Cooperative Oncology Group, treatment with either paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) or carboplatin was associated with an improvement in 1-year survival in patients with stage IV non-small cell lung cancer (NSCLC). Based on these findings, a phase II trial of carboplatin plus paclitaxel was conducted in patients with advanced NSCLC to determine the activity and toxicity of this regimen. Eligibility requirements included stage IIIB or IV histologically confirmed NSCLC, Eastern Cooperative Oncology Group performance status of 0 to 2, no prior chemotherapy, and adequate hematologic, renal, hepatic, and cardiac functions. Paclitaxel was administered intravenously over 24 hours at a dose of 135 mg/m2 (28 patients) or 175 mg/m2 (23 patients), followed by a 1-hour infusion of carboplatin on day 2. Carboplatin was administered at a dose of 300 mg/m2 (16 patients) or, using the Calvert formula, a dose calculated to achieve an area under the concentration-time curve of 6 mg/mL x min (35 patients). Treatment was repeated every 28 days for a total of six cycles. Among the 51 eligible patients, 34 were men and 17 were women; their median age was 60 years and their median Eastern Cooperative Oncology Group performance status was 1. Six patients had stage IIIB and 45 had stage IV disease. Grade 3 or 4 granulocytopenia and thrombocytopenia were observed in 47% and 3% of treatment cycles, respectively. The most common nonhematologic toxicities noted included nausea and emesis, neuropathy, and arthralgia and myalgia. There were no complete responses and 14 partial responses, for an overall response rate of 27% (95% confidence interval, 17% to 41%). Median survival was 38 weeks and the survival rate at 1 year was 32%. Paclitaxel plus carboplatin, as given in this study, was found to be a moderately active regimen in patients with advanced NSCLC. This regimen warrants comparison with existing cisplatin-based regimens in a prospective randomized trial.