FOLFOX/FOLFIRI chemotherapy is usually applied through central venous catheters because of possible occurrence of phlebitis during application of these regimen via peripheral vein. However, the exact frequency and degree of the problems at peripheral venous access site during FOLFOX/FOLFIRI chemotherapy via peripheral vein in the clinical setting has not been reported previously. We investigated the frequency of infusion failure and phlebitis in 43 patients with advanced or recurrent colorectal cancer who received FOLFOX4, mFOLFOX6 or FOLFIRI chemotherapy in our institution. After informed consent, FOLFOX/FOLFIRI chemotherapy was applied via peripheral vein in 29 cases; all courses (13.1+/-8.1 (Mean+/-SD)courses, 5-FU: 3,510+/-743 mg/body/course) were completed via peripheral vein in the 20 cases (70%). In the other 9 cases, the access site was converted to the central vein because of the problems of access site following completion of 5.9+/-2.0 courses via peripheral vein. Fifty eight times of phlebitis were recognized during total of 301 courses; severe phlebitis requiring medical treatment was not recognized in any case. Seventy seven times of the change of venous access site were required during total of 301 courses. These data would be essential for the exact informed consent for choosing the access site for FOLFOX/FOLFIRI chemotherapy.