Background: The aim of this study was to determine the clinical activity and toxicity of a novel chemotherapy combination regimen of gemcitabine plus cisplatin, administered every three weeks, in patients with advanced non-small-cell lung cancer (NSCLC). Patients and methods: Twenty-six previously untreated stages III (14) and IV (12) patients were included. Gemcitabine was administered on days 1 and 8 at a dose 1250 mg/m2 and cisplatin was administered at a dose of 100 mg/m2 on day 1, every 21 days. Results: Twenty-five patients were evaluable for response. One patient achieved a complete response, and 16 patients partial responses. The overall response rate was 65.3% (95% CI: 45%-82%). The main toxicity was hematological: neutropenia NCIC-CTC grade 3-4 in 54% of the patients, and thrombocytopenia grade 3-4 in 23%. The non-hematological toxicity was mild and tolerable. Only 13% of gemcitabine injections were dose-reduced or omitted due to toxicity. The actual dose-intensity of gemcitabine was 715 mg/m2/week, and 31 mg/m2/week for cisplatin. These figures represent the 86% and 93% of the theoretical dose intensity of both drugs, respectively. With a median follow-up of 10 months (range 7-13), 17 patients are still alive and nine have died. The median overall survival is 12 months. Conclusion: This novel combination of gemcitabine and cisplatin administered every three weeks is well tolerated and induces a remarkably high response rate. The regiment proves more interesting than the four- week schedules, particularly regarding patients who are candidates for local therapy.