We calculated age-adjusted incidence rates per 100,000 by religion (Mormon, non-Mormon) for Utah (United States) using the 49,182 cancer cases occurring between 1971-85. For all causes of cancer, the rate in Utah for male members of the Church of Jesus Christ of Latter-day Saints (LDS or Mormons) was about 24 percent less than the comparable US rate. There was a 50-percent lower rate of cancers associated with cigarette smoking among LDS men. Non-LDS (NLDS) men in Utah experienced an incidence of smoking-associated cancers slightly higher than other US men. LDS men had an incidence of those cancers not associated with smoking slightly lower than US men, and NLDS men had a 40-percent higher rate than US men because of higher rates of melanoma and cancers of the lip and prostate gland. LDS women had an all-sites cancer rate 24 percent below the comparable US rate, and a 60-percent lower rate of smoking-associated cancers. The incidence of cancer not associated with smoking was 20 percent lower for LDS women compared with US women and was the result of lower rates of cancers of the colon, breast, and uterine cervix. NLDS women had a 13-percent higher incidence of cancers not associated with smoking because of higher rates of cancers of the lip and breast.