The novel nucleoside agent gemcitabine has demonstrated antitumor activity against a variety of solid tumors and is associated with low toxicity. A phase I trial in Germany of gemcitabine combined with the alkylating agent ifosfamide has shown encouraging activity against non-small cell lung cancer (NSCLC). The efficacy and toxicity of this combination was further evaluated in a phase II trial of chemotherapy-naive patients with NSCLC (mostly stage IV disease). Gemcitabine was administered at a dose of 1,000 mg/m2 on days 1, 8, and 15 followed by a 1-week rest, while ifosfamide was given at a dose of 1,500 mg/m2 on day 8 and days 9 through 12. Fifty-one of 56 patients were evaluable for response. Eleven partial responses were seen, for an overall objective response rate of 22%. The 6- and 9-month survival rates are 62% and 41%, respectively. Grade 3 and 4 neutropenia occurred in 35.8% and 24.5% of patients, respectively, but the incidence of infection was low. These results indicate that the combination of gemcitabine and ifosfamide is active against NSCLC and has a mild toxicity profile, and suggest that further evaluation of this combination is warranted.