The review is based on studies from Denmark, Finland, Norway and Sweden during 1950-1982. In general sarcoidosis was slightly more frequent in females than in males, especially after 40 years of age. The majority of cases were diagnosed before 35 years; 59% had symptoms, 41% were found by chance. Radiological stage I was present in 50%, stage II in 35%, and stage III-IV in 14%. The prevalence was age dependent with maximum between 18-35 years, varying from 8-102/10(5) examined persons in Finland to 27 in Norway and 64 in Sweden. The incidence was likewise age related, being highest in 18- to 20-years-old males (57/10(5) examined persons/year); overall incidence varied from 14-15/10(5) examined persons/year in Denmark, Finland and Norway to 24 in Sweden. No definite change in incidence figures has occurred. The accumulated lifetime risk of acquiring sarcoidosis was identical in the two sexes up to 45 years of age, and then increased in females; at 65 years the risk was 1.6% in females and 1.2% in males based on the population examined.