Colon cancer has been associated with several nutrients and foods. The authors used data from a population-based study conducted in Northern California, Utah, and Minnesota to examine associations between dietary eating patterns and risk of developing colon cancer. Through factor analysis, detailed dietary intake data obtained from 1,993 cases (diagnosed in 1991-1994) and 2,410 controls were grouped into factors that were evaluated for relations with lifestyle characteristics and colon cancer risk. Several dietary patterns emerged. The dietary patterns with the most variation were labeled "Western," "prudent," "high fat/sugar dairy," "substituters," and "drinkers." The "Western" dietary pattern was associated with a higher body mass index and a greater intake of total energy and dietary cholesterol. The "prudent" pattern was associated with higher levels of vigorous leisure time physical activity, smaller body size, and higher intakes of dietary fiber and folate. Persons who had high scores on the "drinker" pattern were also more likely to smoke cigarettes. The "Western" dietary pattern was associated with an increased risk of colon cancer in both men and women. The association was strongest among people diagnosed prior to age 67 years (for men, odds ratio (OR)=1.96, 95% confidence interval (CI) 1.22-3.15; for women, OR=2.02, 95% CI 1.21-3.36) and among men with distal tumors (OR=2.25, 95% CI 1.47-3.46). The "prudent" diet was protective, with the strongest associations being observed among people diagnosed prior to age 67 years (men: OR=0.63, 95% CI 0.43-0.92; women: OR=0.58, 95% CI 0.38-0.87); associations with this dietary pattern were also strong among persons with proximal tumors (men: OR=0.55, 95% CI 0.38-0.80; women: OR=0.64, 95% CI 0.45-0.92). Although "substituters" (people who substituted low fat dairy products for high fat dairy products, margarine for butter, poultry for red meat, and whole grains for refined grains) were at reduced risk of colon cancer, the reduction in risk was not statistically significant. These data support the hypothesis that overall dietary intake pattern is associated with colon cancer, and that the dietary pattern associated with the greatest increase in risk is the one which typifies a Western-style diet.