INTRODUCTION: This phase II study investigated the anti-tumour activity and toxicity of CPT-11 (250 mg/m2 i.v. infusion over 60 minutes) administered every 2 weeks as second-line chemotherapy in patients with advanced colorectal cancer (CRC). MATERIAL AND METHODS: Patients (n = 63) with histology diagnosis of advanced CRC and proven resistance to previous fluoropyrimidine therapy were enrolled. RESULTS: A total of 510 CPT-11 cycles were administered, with a mean of 8 cycles per patient (range: 1-32). The median relative dose intensity was 93%. Partial response (PR) was obtained in 11 patients (17.5%; 95%CI: 8.1%-26.7%) and 29 patients (46.0%) showed stable disease (clinical benefit of 63.5%). The median duration of response was 6.8 months (95%CI: 6.1-7.5 months), median survival was 8.8 months (95%CI: 6.3-11.5 months) and median time to disease progression was 4.5 months (95%CI: 3.9-5.0 months). Overall, this schedule of CPT-11 chemotherapy was well tolerated by the patient. Neutropenia was the most frequent grade 3/4 haematological toxicity (20.6% of patients and 4.1% of cycles). Neutropenia with concurrent fever or infection occurred in 7 patients (11.1%). Late onset diarrhoea was the most frequent grade 3/4 non-haematological toxicity (19.0% of patients and 2.3% of cycles). Other, lower-incidence, toxicities were anaemia, fever, infection, mucositis, nausea and vomiting. There were no toxic deaths. CONCLUSIONS: We found that CPT-11, administered as 250 mg/m2 i.v. infusion over 60 minutes every 2 weeks, was active and well tolerated schedule in the second-line chemotherapy of advanced CRC patients. This bi-weekly scheme could be used as an alternative to the weekly or the every-three-week schedule as well as in combined therapies with other chemotherapeutic agents for the treatment of advanced, metastatic, CRC.