Hospital admission statistics from a district general hospital for patients aged 30-59 years over a 6-year period were analysed. There were 40 034 admissions excluding obstetrics. The overall distribution by place of birth was 9·2% West Indies, 13·5% Asia and 71·9% Northern Europe. This distribution was compared with the distributions for 4 groups of respiratory diseases. There were highly significant differences between these distributions for each diagnostic category. Asthma and respiratory tuberculosis were very much more common amongst Asians whilst West Indians suffered very little carcinoma of bronchus or bronchitis. Data collected from a factory screening showed that cigarette smoking could not account for these differences.