A phase I study was conducted to evaluate the maximum tolerated dose, feasibility, and efficacy of bi-weekly-administered paclitaxel and gemcitabine in patients with non-small-cell lung cancer (NSCLC) who had previously been treated with platinum-based chemotherapy. In a dose-escalation study, 18 patients, under 75 yr old, with unresectable NSCLC that had relapsed or was resistant after platinum-containing chemotherapy with performance status of 0-2 were enrolled. Patients were treated with paclitaxel and gemcitabine bi-weekly. The dose escalation levels of paclitaxel (mg/m2) at a fixed dose of gemcitabine 1000 mg/m2 were 110 (level 1), 130 (level 2), 150 (level 3), and 170 (level 4), respectively. All patients were eligible for evaluation of toxicities. At level 4, one patient developed an infection with grade 3 neutropenia and two other patients developed severe neurotoxicity (over grade 3). Thus, the recommended dose for phase II was paclitaxel 150 mg/m2 and gemcitabine 1000 mg/m2 due to dose-limiting toxicities including neutropenia and peripheral neurotoxicity. Partial response was seen in 4 cases of the 18 assessable patients, with an overall response of 22%. Bi-weekly paclitaxel and gemcitabine is feasible and appears to be an efficacious combination chemotherapy as second-line chemotherapy in refractory and recurrent patients with NSCLC who had been previously exposed to platinum-containing chemotherapy.