A prerequisite for acquiring data on death and illness in chronic obstructive pulmonary disease is the application of agreed operational definitions. The International Union against Tuberculosis and Lung Diseases recommended that International Classification of Diseases 490-496 be grouped together for mortality statistics. A task force of the European Respiratory Society have given operative criteria for chronic obstructive pulmonary disease which depend very much on spirometric reference values collected 25 years ago. The mortality rates in chronic obstructive disease vary more than 5-fold among the European countries. Deaths due to chronic obstructive pulmonary disease as a proportion of all deaths increase greatly with age and are considerably lower in females than in males. Community surveys in countries of both northern and southern Europe indicate that 4-6% of the adult population suffer from clinically relevant chronic obstructive pulmonary disease. The prevalence increases greatly with age; however two-thirds have only a mild reduction in lung function.