We evaluated the efficacy and safety of modified FOLFIRI for patients with refractory advanced or recurrent colorectal cancer. Modified FOLFIRI was given 29 patients (21 men and 8 women, with a median age of 61.0 years) from 2 to 16 times (median 10.0). 19 out of 29 patients were colon cancer, and the other 10 were rectal cancer. 18 patients were administered as first-line chemotherapy, and 11 were more than second line. CPT-11 was administered at a dose of under 150 mg/m(2), to remain within the limits in Japan. The response to treatment was CR in 3 patients, PR in 8, and SD in 12. The response rate was 37.9%. Grade 4 hematologic toxicities included leukocytopenia in 2 patients, neutropenia in 7 and anemia in 1. Grade 3/4 non-hematologic toxicities included febrile neutropenia in 4 patients, anorexia in 3, fatigue in 3, and nausea, diarrhea and interstitial pneumonia in 1. Except in 2 patients, all reactions could be controlled with the use of G-CSF or by setting drug holiday. In summary, modified FOLFIRI is a safe and effective regimen even at a dose of under 150 mg/m(2), of CPT-11. It can be given with good tolerance for patients with refractory advanced or recurrent colorectal cancer on an outpatient basis with due care especially for neutropenia.