CPT-11 (irinotecan) has shown activity in patients with advanced colorectal cancer resistant to leucovorin (LV) and 5-fluorouracil (5-FU). In this study, the simplified bimonthly LV-5-FU regimen was combined with CPT-11 (FOLFIRI) as third-line therapy for patients with advanced colorectal cancer. Continuous infusion of 5-FU was administered with disposable pumps as outpatient therapy. FOLFIRI consisted of CPT-11 180 mg/m2 as a 90-min infusion day 1; LV 400 mg/m2 as a 2-h infusion during CPT-11, immediately followed by 5-FU bolus 400 mg/m2 and 46-h continuous infusion of 2.4-3 g/m2 every 2 weeks. Among the 33 patients treated, 2 had partial responses for an overall response rate of 6%; 20 patients were stabilised (61%) and 11 had disease progression (33%). From the start of FOLFIRI, median progression-free survival was 18 weeks and median survival was 43 weeks. For the 242 cycles analysed, NCI-CTC toxicities grade 3-4 per patient were nausea 15%, diarrhoea 12% and neutropenia 15%. Overall, 10 patients (30%) experienced grade 3-4 toxicity. 7 patients (21%) had grade 2 alopecia. FOLFIRI generated activity and acceptable toxicity, in heavily pretreated patients, with limited diarrhoea, mostly asymptomatic neutropenia and manageable nausea and relatively uncommon alopecia. This regimen is suitable for studies in chemotherapy-naïve patients.