Newly diagnosed colon or rectal cancer should be staged using the TNM (tumor, node and distant metastasis) nomenclature to determine prognostic factors. Based on this staging, it is possible to select patients in need of adjuvant therapy following surgery. In patients with stage III colon cancer, adjuvant chemotherapy with fluorouracil and levamisole has been shown to produce a 40 percent reduction in the recurrence rate at a median follow-up of 6.5 years as well as a 33 percent reduction in mortality. Adjuvant chemotherapy should be considered in all patients with stage III colon cancer and in selected patients with high-risk stage II colon cancer. A 34 percent improvement in disease-free interval and a 29 percent improvement in survival have been reported for patients receiving fluorouracil, methyl-CCNU and radiotherapy. Adjuvant chemotherapy and radiotherapy are indicated in patients with stages II and III rectal cancers.