The aim of the research was to find out if healthy lifestyle influences the longevity. The group of 906 monks and 866 nuns who worked and died in Poland in the years 1950-2000 was regarded as people who conducted a healthy lifestyle. The population of adult Poles was chosen as a control group. As a result of the research it is reported that: 1) since 1950 till middle 1960's people in monasteries lived shorter than adult Poles [in the first ten years of the research the average life span of monks was 2.4 years shorter (t162 = 1.99, p = 0.047) and nuns lived 9 years shorter (t56 = 4.2, p < 0.001)], since the middle of 1970's till the end of 1980's the group in question lived as long as the general population, finally, for the last ten years of the investigated period of time people in monasteries lived longer [monks 2.5 (t219 = 2.5, p < 0.05), nuns 2.9 years longer (t209 = 4.6, p < 0.001)]; 2) since 1950's till 2000 the average life span in the investigated group of both sexes was increasing at the rate of 0.175 (t98 = 3.9, p < 0.001) years per calendar year greater than this value in the general population and there is no reason to assume that there have been differences between sexes; 3) as far as men are concerned, joining a monastery in the case of man enter into the monastery a year earlier prolongs life for about 0.1 year (F1,842 = 3.8, P one side test = 0.026). In case of women this relation was not significant (F1,804 < 0.1). The shorter life of people in monasteries after the second world war might be interpreted as a result of their socio-political situation at that time. In the course of time their standard of living and the access to medical treatment has been improving gradually, so their longevity is increasing faster. In the context of the investigated problem the most important results were obtained from the last ten years. These results indicate that healthy lifestyle prolongs life.