Feces collected in Kuopio, Finland, a low-risk population for colon cancer, and in the New York metropolitan area, a high-risk population for colon cancer, were compared. The dietary intake of fat and protein were the same in the two populations, but the sources of fat were different, a greater portion coming from meat in New York, and from dairy products in Kuopio. The daily stool output was higher in Kuopio due to the high intake of cereal products rich in fiber. The concentration of fecal secondary bile acids and the bacterial beta-glucuronidase activity were lower in Kuopio, but the daily output of these constituents was the same in the two groups. The daily fecal excretion of neutral sterols was higher in Kuopio than in New York. Our data suggest that the greater fecal bulk in Kuopio may dilute tumorigenic compounds which come in direct contact with the colon mucosa.