Colorectal cancer is the second leading cause of cancer death in Western countries. If surgery remains the only cure, recurrence rates for colon cancer range from 30% to 60% for stage III tumors. Adjuvant chemotherapy is the standard treatment for stage III colon tumors and consists of monthly administration of bolus 5-fluorouracil and leucovorin for 5 consecutive days a month over a 6-month period (Mayo regimen). Adjuvant chemotherapy for stage II colon cancer remains controversial, and its administration is not routinely recommended except in certain high-risk and selected patients. Immunotherapy, new drug-based therapies or combinations, and cyclooxygenase-2 inhibitors are being tested in the adjuvant setting. Total mesorectum excision is now the gold standard surgical technique for rectal cancer resection, and this procedure has dramatically decreased local recurrence. Nevertheless, adjuvant chemoradiotherapy is commonly indicated in the United States. In Europe, neoadjuvant radiotherapy is recommended for stage II and III resectable rectal cancers; the role of chemotherapy remains mostly investigational.