The population living within a small area around a sulphite pulp factory in Northern Sweden was studied with regard to chronic obstructive lung disease. In persons in the age group 20-64 years the prevalence of bronchial asthma was found to be 3.0% for males and 3.2% for females. These figures correspond closely with previous studies in the Central and Southern Sweden. In the same age group the prevalence of chronic bronchitis was 2.8% for males and 1.0% for females, i.e. not differing much from that of other parts of Sweden. These findings, however, were far removed from the high prevalence of chronic bronchitis reported from Northern Finland, viz. 28.2% in males and 5.8% in females. The difference is probably attributable to differences in diagnostic criteria. In this study, those sulphite pulp factory workers who smoke seemed to constitute a population running a high risk of contracting chronic bronchitis.