The health effect of being a Seventh-day Adventist was studied by computer-linking the official church rosters with National Health Registries. Birth weight in children born by Seventh-day Adventist mothers was 99 g higher (P < 0.001) than that of matched control subjects. Total cholesterol was 0.86 mmol/L lower in the Seventh-day Adventist men (P < 0.001) and 0.48 mmol/L lower in women (P < 0.001). Cancer incidence was not significantly lower in Seventh-day Adventists [standardized incidence ratio (SIR) in men, 91; women, 97]. Total mortality was significantly lower only in Seventh-day Adventist men [standardized mortality ratio (SMR), 82; P < 0.001], especially cardiovascular mortality. Entering the church at an early age had a large effect on later mortality. The study supports previous findings in Seventh-day Adventists, with the exception of cancer incidence and mortality. An early establishment of a healthy lifestyle seems to be of decisive importance in the risk of later disease.