We evaluated the antitumoral efficacy and safety of CPT-11 125 mg/m2 (weekly 90 min i.v. infusion; days 1, 8 and 15) combined with UFT (oral combination of tegafur and uracil) 200 mg/m2/day plus leucovorin (LV) 45 mg/m2/day (both divided into three separate oral doses every 8 h, days 1-21) every 4 weeks as first-line chemotherapy of metastatic colorectal cancer (CRC). Fifty-three patients > or =18 years old with histologically confirmed diagnosis of advanced CRC and bidimensionally measurable disease were enrolled. Three patients (6%) showed CR and 8 patients (15%) showed PR (ORR = 21% (95% CI, 10-32). Stable disease was reported in 19 patients (36%) [tumor control rate = 57% (95% CI, 43-70)]. The median time to progression and overall survival were 7.9 and 18.2 months, respectively (1-year rate = 74%; 2-years rate = 26%). CPT-11/UFT/LV treatment was well tolerated: the most reported grade 3/4 toxicities were neutropenia (11% of patients) and delayed diarrhea (28% of patients). No significant differences in response rate, survival or toxicity were found between younger (< or =65 years) and older patients (> 65 years). Weekly CPT-11 plus UFT/LV was found effective and safe as first-line chemotherapy for metastatic CRC. The addition of CPT-11 to UFT/LV doubled the response rate compared to the results previously reported with UFT/LV, while myelosuppression remained low.