The purpose of this study was to compare the activity and toxicity of an irinotecan (CPT-11), leucovorin (LV) and 5-fluorouracil (5FU) combination with a standard regimen of 5FU and LV, in patients with advanced colorectal carcinoma. One hundred and sixty patients were randomized; 80 patients (group A) received LV 20 mg/m(2) bolus i.v. and 5FU 425 mg/m(2) bolus i.v. on days 1-5, every 28 days; 80 patients (group B) received CPT-11 80 mg/m(2) (30-90 min i.v. infusion), followed by LV 20 mg/m(2) bolus i.v. and 5FU 425 mg/m(2) bolus i.v. on days 1, 8, 15, 22, 29, and 36, every 8 weeks. The overall response rate was 30% and 47.5% in groups A and B respectively. Progression-free survival was significantly higher in the triple-drug combination arm (median 7.5 vs. 4.5 months; p= 0. 0335). However, overall survival did not differ significantly between the two arms (15 months vs. 14 months for the groups B and A respectively; p=0.3531). The main grade 3 adverse events were diarrhea (19%, in group A vs. 35% in group B; p=0.032) and mucositis (2% vs. 14%; p=0.017). The regimen containing irinotecan showed activity in advanced colorectal cancer. The overall safety data confirm this combination as a well-tolerated treatment.