It has been estimated that 80--90% of the cancer rate in the U. S. can be attributed to environmental factors. For the last 20 years the role of smoking has been recognized by the scientific community. However it is only recently that the role of diet, i.e., food and beverages in carcinogenesis has begun to be recognized. It is likely that diet is more important than smoking in cancer causation. Both human and animal studies support this assumption. The study of special populations in the U. S. such as the Mormons and the Seventh Day Adventists also point to the potential of reducing U. S. cancer rates and individual risk factors through the modification of dietary habits. The major hypotheses of the role of dietary and nutritional factors in cancer etiology are examined in light of current scientific knowledge. General guideline for the reduction of risk from the major chronic diseases are also discussed.