Give up cigarettes and eat a low-cholesterol, low-fat diet and you will eliminate the major risk factors in cancer, says Dr. Whelan, an epidemiologist at the Harvard School of Public Health. But she is quick to point out that the reasons for taking these steps differ. Tobacco has been indicted on the basis of strong statistical evidence, animal studies, dose-response relationships. Rich diets are suspect on the basis of epidemiological studies (differences between American and Japanese eating habits, for example) and the relation between fats and hormone production. In turn, Dr. Whelan discusses the evidence linking alcohol, radioactivity, sun, drugs, sex (cervical cancer), and occupation to cancer. Here the case histories and other evidence provide strong reasons for the proscriptions, cautions, or moderation (in the case of alcohol) that Whelan presents at the end of each chapter. The second, more speculative part of the book deals with saccharin, air pollution, stress, food additives, and personality as causal factors in cancer. Surprisingly, she takes a more lenient stance here. She finds no excuse for banning cyclamates or Red Dye #2, for example, and would not eliminate DES as a cattle growth stimulant (she does not discuss hormone additives in poultry). She even finds sugar innocent of any systemic disturbance. The Delaney clause should be rescinded, she contends. (It imposes a ban on additives or pesticides if they are tumor-producing in any one animal species.) While one agrees that the present climate may be one of overreaction and cancerphobia, it would seem more prudent not to be so quick to give a clean bill of health to these chemicals. Cancer poses the difficult problem of a long delay between exposure and disease, and it is not clear that some chemicals are ever safe at any level. So while the book's intent to present an optimistic and self-monitoring approach to cancer prevention is praiseworthy, Dr. Whelan's own convictions in the more controversial areas are just that--controversial.