Colorectal cancer, one of the most common human malignancies, is also one of the best understood. The epidemiology of this disease, and its relationship to environmental influences, particularly diet, has been extensively studied. New insights into the molecular biology and genetics of colorectal cancer also provide clues to its etiology, and high-risk populations that are most likely to benefit from preventive measures can be identified. Using this information, promising strategies for prevention of colorectal cancer are under investigation. These strategies include dietary modification, screening and adenoma removal, and antitumor agents from both natural and synthetic sources.