This is a controlled study designed to compare relapse-free survival and overall survival in patients receiving UFT with those in patients receiving surgery alone. Patients will be randomly assigned to surgery alone or surgery followed by UFT within 6 weeks after curative resection. To assess treatment efficacy, data on recurrence and survival will be collected for 5 years after enrollment of the last patient. To evaluate safety, data on adverse events will be collected for 12 months after the start of treatment.Evaluations will be separately done for colon cancer and rectal cancer.

Inclusion Criteria:

• Age 20 to 75
• Performance status 0 , 1, or 2 (ECOG)
• Hematopoietic WBC ≥ 4,000/mm^3 Platelet ≥ 100,000/mm^3
• Hepatic AST and ALT ≤ 2 times upper limit of normal(ULN) Total bilirubin ≤ 1.2mg/dL
• Renal BUN ≤ 25mg/dL Creatinine ≤ 1.5mg/dL

Exclusion Criteria:

• Prior anticancer treatment