Gemcitabine is active against non-small cell lung cancer (NSCLC), with single-agent response rates of 20% or more in previously untreated patients. Its mild toxicity profile suggests that it should be well tolerated by older patients. To assess the impact of age on the efficacy and tolerance of gemcitabine, the results of four phase II trials of single-agent gemcitabine for the treatment of NSCLC were analyzed retrospectively. Starting doses for gemcitabine ranged from 800 to 1,250 mg/m2/wk, and in all studies gemcitabine was administered weekly for 3 weeks followed by a 1-week rest period. Response rates, toxicity, and dose delivery were compared for two age groups, less than 65 years (255 patients) or > or = 65 years (105 patients). The pretreatment characteristics for both patient groups were well balanced. Overall response rates were 16% and 24% for the younger and older patients, respectively (P = .072). Median survival and 1-year survival rates were 8.1 months and 27% and 9.1 months and 36%, respectively, for patients aged less than 65 years and > or = 65 years. Hematologic and nonhematologic toxicities were similar for both age groups. The number of cycles associated with dose reductions or dose omissions and the mean number of treatment cycles administered were also similar. In summary, gemcitabine is active and well tolerated in elderly patients with NSCLC, and is a promising new alternative for the treatment of this patient population.