The adjuvant therapy of colorectal cancer has seen many important advances in recent years. Chemotherapy improves long-term disease-free survival rates in high-risk patients with resected colon cancer. Combined modality therapy, using surgery, radiation therapy, and chemotherapy, improves both local control and survival in patients with stage II and III rectal cancer. We examine in detail the data on which current recommendations for adjuvant treatments are based. We also review some of the more promising experimental approaches currently under investigation.