The occurrence of various types of cancer have been reviewed and evaluated in 4 religious groups. These patterns have been critically assessed in light of the distinctive life-style features of these groups. All 4 religious groups considered in this paper have reduced overall rates of cancer, suggesting that the life-styles of all 4 groups have merit in terms of reducing the overall risk of cancer. The rate of smoking among these groups is nearly nil, and the lung cancer rate in all 4 of these religious groups is strikingly low. Cancer of the oral structures, pharynx, larynx, and esophagus is also generally quite low. Amish and Hutterites have unusually high rates of breast cancer and juvenile leukemia. Reproductive factors frequently mentioned as risk factors for breast cancer cannot explain the excess breast cancer in the Amish and Hutterite women because they should have had the effect of reducing the rate. None of the numerous risk factors, normally suggested for leukemia, are consistent with this observation. The observations on ovarian cancer tend to confirm low parity and late age at first birth as risk factors, although the evidence is not entirely consistent. Also, contrary to common observations, the pattern of ovarian cancer contrasts greatly with the breast cancer pattern, suggesting dissimilar risk factors. Their low rate of cervical cancer is consistent with promiscuity being a strong risk factor, but other frequently suggested risk factors were generally inconsistent with the observations. Cancers of the stomach, colon, rectum, urinary bladder and prostate, in these 4 religious groups, are not readily explained by the risk factors commonly implicated in cancer of these sites. The patterns of a few types of cancers were consistent with the prevailing opinions of risk factors, but some cancers were poorly explained and, in some cases, the cancer patterns contradicted commonly held opinions concerning risk factors. Religions that provide strong directives for the personal lives of adherents result in distinctive life-style, reflecting multiple disease related factors (risk factors and protective factors). Disease related factors are related to each other in simple or more complex ways (e.g. additive, multiplicative or even more complex). Therefore, when dealing with distinctive life-styles, it may be unwarranted to attempt to isolate individual risk factors.