This 2 arm study will compare the safety and efficacy of oral Xeloda, or 5-fluorouracil in combination with leucovorin, in patients who have undergone surgery for colon cancer. Patients will be randomized to receive either Xeloda 1250mg/m2 po bid on days 1-14 every 21 days, or leucovorin 20mg/m2 iv + 5-fluorouracil 425mg/m2 iv daily from day 1 to day 5 every 28 days. The anticipated time on study treatment is 3-12 months, and the target sample size is 500+ individuals.