Although it is generally believed that a simple lifestyle may promote health, a recent study among Trappist and Benedictine monks in the Netherlands reported an increase in general morbidity (Am J Epidemiol 1993; 138:569-73). As this increased morbidity might be the consequence of an increased life expectancy, we studied the level of mortality among these contemplative monks. Standardized mortality ratios (SMRs) and death rates were calculated from 1,523 monks whose data were abstracted from the monastery rolls of theperiod 1900-1994. For this period the SMR was 0.88 (95% confidence interval (Cl) 0.81–0.95). A lower SMR was present in almost all of the age categories and in all except one of the monasteries. There were two distinct subperiods. In the pre-Worid War II era, the SMR was 1.25 (95% Cl 1.04–1.49), but it lowered to 0.76 (95% Cl 0.69–0.85) after World War II. From 1950 on, mortality in the monasteries remained lower than in thegeneral population, even after correction for the generally higher educational level of the monks. The death rates showed a continuing decline from 1900 to 1950. After 1950, the mortality among monks declined further at a time when the secular trend of decreasing mortality leveled off in the general male population. The higher mortality before World War II was largely unexplained. From the 1950s onward, the mortality among monks was lower, presumably because of the epidemic of lung cancer and cardiovascular disease in the general population. Taken together, the present and earlier data suggest that, among contemplative monks, a simple lifestyle is associated with an extension of life in which they suffer from nonfatal morbidity.