A dose escalation study of paclitaxel in combination with vinorelbine was conducted in 21 patients with previously untreated stage IIIb or IV non-small cell lung cancer (NSCLC). All three patients treated with the initial dose of paclitaxel 135 mg/m(2) administered as a 1-h intravenous infusion and vinorelbine 25 mg/m(2) experienced dose-limiting toxicity (febrile neutropenia). After modification of the dosing schedule, the MTD of paclitaxel was found to be 115 mg/m(2) when combined with vinorelbine 20 mg/m(2) on day 1, followed by vinorelbine 20 mg/m(2) on day 5. Partial responses were achieved in 24% of patients, with a median duration of response of 126 days (range from 84 to 484 days) and a 1-year survival rate of 42%. In conclusion, haematologic toxicity (febrile neutropenia/neutropenia) severely restricts the dosing schedule of combined paclitaxel and vinorelbine, and possibly limits anti-tumour efficacy.