Alpha-1-antitrypsin (alpha 1-AT) phenotypes and serum levels were measured in 518 employees at a sulphite pulp factory. There were 439 men and 79 women with the mean age of 42 years (range 18-65 years). Mean time of employment at the factory was 17.5 years and 216 (42%) individuals had been employed for more than 20 years. Chronic bronchitis was present in 47 (9.1%) individuals. alpha 1-AT rare types (MZ, MS, MF) were present in 12.8% of the individuals with chronic bronchitis compared to 8.4% in employees with no respiratory symptoms, the difference being not statistically significant. Individuals with chronic bronchitis and rare types were evenly distributed with regard to work place at the factory. Serum levels of alpha 1-AT were somewhat higher in smokers compared to non-smokers, but the difference was not statistically significant. Exposure to SO2 and chlorine did not seem to affect the serum levels of alpha 1-AT in M type individuals. In the present study, individuals heterozygous for alpha 1-AT deficiency phenotypes (MZ, MS, MF) did not seem to have an increased rate of chronic bronchitis. However, the rate of chronic bronchitis in factory employees was significantly increased compared to that among non-employees in the surrounding community. This increase appears to be due to a higher rate of smoking and to occupational exposure (SO2 and chlorine) among the sulphite pulp factory workers.