The epidemiological evidence supporting hypotheses concerning colorectal carcinogenesis presents conflicting findings. Even the detrimental role of high fat intake and the protective effect of fibre have to be qualified. In order to improve knowledge on the etiopathogenesis of colorectal cancer, more attention should be directed to the modifiers of the action of carcinogenic or anticarcinogenic substances. Sex, age, hormonal and metabolic status should be precisely accounted for, as should the exact anatomical subsite of the cancer.