We carried out a single-center series with the combination of irinotecan (CPT-11) plus protracted 5-fluorouracil (5-FU) infusion as second-line chemotherapy for patients previously treated with a single-agent fluoropyrimidine as monotherapy or in combination with oxaliplatin. Twenty-five patients diagnosed with advanced colorectal cancer (CRC) received CPT-11 300 mg/m2 every 3 weeks plus 5-FU 250 mg/m2/day as a protracted infusion. Results were as follows. Twenty-four of 25 patients were evaluable for response. Two patients achieved a complete response and five a partial response, resulting in an overall response rate of 28%. Disease stabilization was obtained in 10 patients (40%), resulting in a tumor growth control rate of 68% (17 patients) and disease progression in seven (28%). Median progression-free interval was 6 months and median overall survival was 12 months. Neutropenia and diarrhea appeared as the most frequent adverse events, being grade 3/4 in 12 and 16% of patients, respectively. Mucositis, emesis, and hand and foot syndrome were mild. We conclude that protracted 5-FU infusion plus CPT-11 is an active and safe regimen for patients with advanced CRC. A phase III trial comparing this schedule with conventional CPT-11 monotherapy is warranted.