Asthma is one of the few diseases which has been reported to be common in the higher social classes. In order to assess the relationship between severe asthma and social class we analysed a national study of disabled adults undertaken by the Office of Population Censuses and Surveys (OPCS). The study estimated that there were 5.8 million people over 16 years with some degree of disability living in private households in England and Wales. Thirteen percent of disabilities were due to respiratory disease: 6% chronic bronchitis and emphysema, 3% asthma and allergy, and 4% other respiratory diseases. Among 10,000 individuals interviewed, 338 disabled adults reported asthma as a contributing cause of their disability. Of 291 cases with social class recorded, 41 (14%) were in social classes 1 and 2, 128 (44%) in social class 3, and 122 (42%) in social classes 4 and 5. An estimate of the relationship between social class and adult asthma in the general population was derived by calculating a morbidity ratio for the different social classes. The morbidity ratio for all social classes combined equals 100: for social classes 1 and 2 it was 63 (95% confidence intervals 48, 91); 93 (95% confidence intervals 77, 109) for social class 3; and 131 (95% confidence intervals 108, 153) for social classes 4 and 5. Adults in social classes 4 and 5 were approximately twice as likely to have severe asthma as those in social classes 1 and 2. This could be as a result of differences in the prevalence or treatment of asthma among the social classes.