2,550 persons from a geographically delimited area in Sweden were examined and described by a team of 4 psychiatrists in 1947. Mental disorders, personality traits, social factors, etc. were recorded for all but 1% of the population. 10 and 25 years later the same persons were examined in the same way irrespective of domicile. Great efforts were made to get sufficient outside information about the living as well as the deceased persons. The incidence of age psychoses was lower in the 15-year period 1957–1972 than in the 10-year period 1947–1957.