A normal Finnish population cohort, originally aged 15-64 years, has been followed psychiatrically for 16 years. In the 16-year follow-up, 742 of the original sample of 1000 persons could be contacted and personally examined i.a. by means of the full 140-item version of the PSE. The age-adjusted prevalence of mental disorders in the population aged 30-80 years was 9.9% (6.9% in men and 12.4% in women). The prevalence of psychotic conditions was exceptionally high in comparison to other studies, 2.7%. The occurrence of mental disorders was associated with marital status and social class in men but not in women. Other factors examined, namely age, education, occupational category and experience of unemployment during the follow-up period, were not associated with the occurrence of mental disorders. The results are compared with the results from other studies using the same case finding method.