A phase II trial of UFT (Tegafur and Uracil) modulated by leucovorin was undertaken by the Oncopaz Cooperative Group to assess the efficacy and toxicity of this combination in patients with advanced colorectal cancer. A total of 75 patients were given 500 mg/m2 intravenous leucovorin and 195 mg/m2 of oral UFT on day 1, followed by oral leucovorin 15 mg/12 h and 195 mg/m2/12 h of oral UFT on days 2-14. An overall response rate of 39% was obtained, with seven complete responses (9%), and 22 partial responses (29%). The primary toxicity was gastrointestinal, with grade 1-2 diarrhea occurring in 8.5% of courses, and grade 3-4 in 3.5%. Hematologic toxicity was minimal, and there were no deaths due to toxicity. This regimen was active and well tolerated in patients with advanced colorectal cancer, including those 70 years of age or older.