Persuasive data exist as to the importance of environmental factors in the pathogenesis of sporadic colorectal cancer. One possibility is that the effect of environmental factors varies between individuals, perhaps on the basis of inherited variation (polymorphism) in genes which influence the activation or inactivation of dietary carcinogens. Thus far, the focus has been on acetylator genes (NAT1, NAT2) and the activation of heterocyclic amines, carcinogens generated by cooking meat for prolonged periods at high temperature. Three case-control studies and one prospective study have shown a consistent trend towards higher risks for cancer with higher intakes of meat in rapid acetylators for NAT1, NAT2 or both genotypes. Other links between meat, cooking methods, metabolic genotypes and risk for cancer might include enhanced activation of polycyclic aromatic hydrocarbons and N-nitroso compounds by variant genotypes of CYP1A1 and CYP2E1, respectively, and modulation by meat of the protective effect of the E4 allele of apolipoprotein E on risk for cancer of the proximal colon.