A cross-sectional population study. Scand J Work Environ Health 12 (1986) 561-566. In order to study the number of persons previously exposed to asbestos in the general population, an investigation with a self-administered questionnaire and a screening with 10 X 10-cm chest radiographs was conducted among 28,216 men aged 40 years and over in nine municipalities in the county of Telemark, Norway. Among the 21,453 subjects who answered the questionnaire in the primary screening, 3,888 (18.1%) reported previous occupational exposure to asbestos. Of the exposed subjects 2,368 (61.4%) were less than 60 years of age, and 2,611 (69.9%) had been exposed for the first time after 1950. In regard to the degree of exposure, 77.7% considered their previous exposure to be light. Past and present smoking habits were recorded for all the subjects, and a high-risk group of 1,734 subjects with past exposure to asbestos and present smoking was identified. Approximately 270 incident cases of lung cancer can be expected among the 21,453 study subjects during the next 10 years, and it is estimated that about 110 of these cases will occur in the high-risk group with combined asbestos-cigarette exposure.