OBJECTIVE To estimate the safety, activity, and impact on quality of life of a combination of gemcitabine and pemetrexed in patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) in the context of a randomized two-stage phase II study. METHODS Patients in stage IIIB or IV NSCLC were randomly allocated to receive either gemcitabine 1250 mg/m(2) on day 1, and pemetrexed (Alimta) 500 mg/m(2) followed by gemcitabine 1250 mg/m(2) on day 8 of a 3-weekly cycle (GA arm), or paclitaxel 120 mg/m(2) followed by gemcitabine 1000 mg/m(2), both given on days 1 and 8 of a 3-weekly cycle (PG arm). RESULTS 105 (GA arm, 51; PG arm, 54) eligible patients (stage IV, 32 and 30, respectively) were enrolled into this study; thereafter, accrual was stopped due to first-stage analysis. The response rate was 20% (95% confidence interval [CI], 10-33%) in the GA arm, and 32% (95% CI, 20-46%) in the PG arm. Median progression-free survival was 5.1 (95% CI, 3.7-6.5) months in the GA arm, and 8.3 (95% CI, 5.9-10.7) months in the PG arm, while median overall survival was 10.5 (95% CI 7.1-13.9), and 13.3 (95% CI 11.7-14.9) months, respectively. Severe neutropenia (36% vs 22%), and febrile neutropenia (14% vs 7%) were more common with the GA regimen, while hair loss (52% vs 16%) and any grade peripheral neuropathy (31% vs 2%) occurred more frequently with PG regimen. Other severe side effects of GA regimen were diarrhoea (10%), liver enzyme derangement (10%), and fatigue (8%). CONCLUSIONS The GA regimen was tolerated and moderately active in advanced or metastatic NSCLC. However, this combination did not yield any advantage in comparison with the PG regimen, and does not deserve further evaluation.