We analysed data from the Copenhagen City Heart Study to study the prevalence, possible risk factors for, and inter-relations between bronchial hypersecretion (BH) and chronic airflow limitation. The study sample consisted of 12,698 subjects between 20 years and 90 years of age, randomly selected from the population of the city of Copenhagen. The age-adjusted overall prevalence of BH in the population of Copenhagen was estimated to be 10.1%; 12.5% in men and 8.2% in women. The overall prevalence of clinically relevant chronic airflow limitation (forced expiratory volume in 1 s less than 60% of that predicted) was 3.7% and not significantly different between sexes. Both airflow limitation and BH increased with age, smoking, alcohol consumption, short education, and low income. However, the association of airflow limitation with alcohol consumption, education and income was much weaker than the association with smoking. Regardless of smoking habits, the majority of subjects with airflow limitation did not report symptoms of bronchial hypersecretion.