Among precancerous conditions in the colon and rectum, adenomas are the most important, paradigmatically so in adenomatosis coli, a genetic predisposition of autosomal dominant type. Statistical relevance is also attributed to long-term ulcerative colitis, Morbus Crohn, and Gardner's syndrome. Dietary factors seem to play an essential role. Highly developed countries in Western Europe and North America whose prevalence rates of colorectal carcinoma are highest, also have a particularly high daily intake of fat and meat. The proportion of fibers in a diet shows an inverted correlation with the prevalence of colorectal carcinoma. Many epidemiologic data are still rather inconsistent and in some cases rather weak. Detailed case-control studies are needed to substantiate the general statement: Our life style, especially our daily food, is obviously related to the rise of colorectal carcinoma.