Chemotherapeutic combination regimens for advanced non-small cell lung cancer traditionally have been based on platin compounds. However, a mechanistic rationale could lead to effective non-platin combinations. Paclitaxel and vinorelbine are antimicrotubule agents with different mechanisms of action, both of which have single agent activity against non-small cell lung cancer. A Phase I/II trial of paclitaxel Day 1 and vinorelbine Days 1-3 every 21 days was, therefore, performed for patients with Stage IIIB or Stage IV non-small cell lung cancer who had not previously received chemotherapy for metastatic disease. In the Phase I investigation, up to 4 patients were treated at each dose level. The maximum tolerated dose level was found to be paclitaxel 150 mg/m2 IV Day 1 and vinorelbine 16 mg/m2 IV Days 1-3, with dose-limiting toxicities of fatigue, myalgia, and mucositis at higher doses. This dose level was then expanded with an additional 15 patients. Of the 23 patients treated for up to 10 cycles at or near the maximum tolerated dose level (19 patients with paclitaxel 150 mg/m2 IV Day 1 and vinorelbine 16 mg/m2 Days 1-3, and 4 patients with paclitaxel 150 mg/m2 IV Day 1 and vinorelbine 13 mg/m2 Days 1-3), 7 patients achieved partial response and 5 patients achieved minor response. Fatigue, myalgia, peripheral neuropathy, and transient leukopenia were the most common cumulative toxicities seen. The non-platin chemotherapy doublet of paclitaxel and vinorelbine given on this convenient 3-day schedule is worthy of further investigation in the treatment of non-small cell lung cancer.