The efficacy of the protracted infusion of 5-fluorouracil (FU) 200 mg/m2/day admixed with leucovorin (LV) 20 mg/m2/day was assessed for the treatment of advanced colorectal and breast cancer patients. Of 19 patients who underwent heavy treatment, 4 patients demonstrated partial response, 13 become stable and 2 failed to respond to therapy. The overall duration of response ranged from 1.5 to 15.8 months (median 4.5 months) and the survival ranged from 1.7 to over 21.7 months (median 8.2 months). The toxic effects, specifically mucositis, oral ulcer and acral hyperpigmentation, were mild to moderate in grade. Myelosuppression with grade I leucopenia was observed in all the patients. Catheter-related complications such as thrombosis or infection occurred in 4 patients. No death relating to therapy was reported in this study. Continuous intravenous infusion chemotherapy with an admixture of LV and FU is not associated with severe toxic effects when treatment is closely monitored and appropriately administered. This treatment regimen may have some significant benefit in advanced colorectal and breast cancer patients.