This phase II trial was performed to evaluate the efficacy and tolerability of oral tegafur-uracil (UFT) with leucovorin (LV) combined with intravenous (i.v.) irinotecan every 3 weeks (TEGAFIRI) as first-line treatment for patients with metastatic colorectal cancer (mCRC). Patients received oral UFT 250 mg m(-2) day(-1) and LV 90 mg day(-1) in three divided daily doses for 14 days followed by a 1-week rest and i.v. irinotecan 250 mg m(-2) as a 90-min infusion every 3 weeks. Tumour responses, assessed every two cycles using RECIST criteria, were reviewed by an independent review committee. In 52 evaluable patients, the best overall response rate was 33% (95% confidence intervals (CI) 20-47%; 1 complete and 16 partial responses). The median time to progression was 5.4 months (95% CI 3.02-7.52 months) and median overall survival was 14.9 months (11.73-17.97 months). A total of 307 cycles were administered, with a median number of five cycles per patient (range: 1-10). The most common grade 3/4 toxicities were neutropenia (25% of patients), diarrhoea (22%), vomiting (11%) and anaemia (11%). The TEGAFIRI regimen is a feasible, well-tolerated and convenient treatment option for patients with non-resectable mCRC.