The study aims to survey the mortality from asthma in different occupations among Swedish men. The design was a register based cohort study where the smoking adjusted mortality due to asthma among Swedish men 1971-80 was investigated. For each occupation a smoking adjusted standardised mortality ratio (SMR) was calculated based on a linkage between official mortality statistics 1971-80 and occupational information in the 1970 national census. The information about the smoking habits among different occupations was obtained from a smoking survey carried out in 1963. In the statistical analysis only occupations with more than 10 deaths were considered. A significantly increased mortality from asthma was found among farmers (smoking adjusted SMR 137, 95% confidence interval (95% CI) 115-156), farm workers (smoking adjusted SMR 170, 95% CI 107-235), woodworking machine operators (smoking adjusted SMR 226, 95% CI 108-344), clerical workers (smoking adjusted SMR 161, 95% CI 102-220), packers and labellers (smoking adjusted SMR 144, 95% CI 100-188), and watchmen (smoking adjusted SMR 212, 95% CI 104-320). Exposure to organic dust, such as fresh wood dust and dusts in the farming environment, may cause increased mortality due to asthma.