Preliminary results show that the 1970-72 cancer mortality rate among California Mormon adults is about one-half to three-fourths that of the general California population for most cancer sites, including many sites with an unclear etiology. Furthermore, the cancer death rate in the predominately Mormon state of Utah is about two-thirds to three-fourths of the United States rate, and the lowest in the entire country. Mormons are a large, health-conscious religious group whose Church doctrine forbids the use of tobacco, alcohol, coffee, and tea, and recommends a nutritious diet. Initial indications are that Mormons as a whole smoke and drink about half as much as the general population, and that active Mormons abstain almost completely from tobacco and alcohol. However, they appear to be fairly similar to the general white population in other respects, such as socioeconomic status and urbanization. The significance of these findings is discussed.