We examined the safety and efficacy of the combination of docetaxel and irinotecan administered biweekly in patients with refractory or relapsed advanced non-small cell lung cancer (NSCLC). Patients with previously treated NSCLC of stage III or IV were eligible if they had a performance status of 2 or less, were 75 years or younger, and had adequate organ function. From May 2003 through February 2006, 35 patients (27 men and 8 women; median age 64 years; age range 41-75 years) were enrolled. Patients were treated every 4 weeks with docetaxel (33 mg/m(2) on days 2 and 16) plus irinotecan (50 mg/m(2) on days 1 and 15). None of the 35 patients achieved a complete response, but five achieved a partial response, for an overall response rate of 14.3% (95% confidence interval, 4.8-30.3%). The median survival time was 8 months (range 2-29 months). The median time to progression was 3 months (range 1-12 months). Grade 3 to 4 hematologic toxicities included leukopenia in 48.6% of patients, neutropenia in 54.3%, and anemia in 25.7%. No patients had grade 3 to 4 diarrhea or nausea and vomiting. Although one patient had grade 3 drug-induced interstitial pneumonia, all side effects were manageable, and there were no treatment-related deaths. In conclusion, the combination of docetaxel and irinotecan administered biweekly is a safe and effective treatment for refractory or relapsed NSCLC. However, the search for even more active regimens should be continued.