A phase I/II study was conducted to determine the maximum-tolerated dose, the safety and tolerability, and the clinical efficacy of carboplatin and docetaxel in combination in patients with stage IV non-small-cell lung cancer. Patients with measurable, previously untreated, good performance status, and stage IV non-small-cell lung cancer were eligible. Increasing doses of docetaxel were given in combination with a fixed dose of carboplatin except at level 5. Cycles were repeated every four weeks. Seventy-seven patients were registered. In phase I, 27 patients were entered at five different dose levels. A docetaxel dose of 60 mg/m(2) and carboplatin area under the concentration time curve 6 was recommended for phase II, and an additional 50 patients were entered at this level for a total of 56 patients. Grade 3/4 neutropenia was the most common adverse event and occurred in 70% of the patients. Two patients had febrile neutropenia. Fifty-six patients were assessable for response; 21 partial responses were observed for an overall response rate of 37.5%. The median time to tumor progression was 4.0 months (range, 1.0-21.0 months), and the median survival was 12.9 months (range, 0.4-51.3 months). The one-year survival rate was 46.4%. The combination of docetaxel 60 mg/m(2) and carboplatin area under the concentration time curve 6 is feasible and effective in patients with stage IV non-small-cell lung cancer.