The contribution of workplace exposures to the prevalence of asthma in adults has been minimized in the epidemiology of this illness. Analysis of the 1978 Social Security Disability Survey provides a population-based assessment as a novel approach utilizing self-attributed, occupationally related asthma as a measure of disease. Of 6,063 respondents, 468 (7.7 percent) identified asthma as a personal medical condition; 72 (1.2 percent [15.4 percent of all those with asthma]) attributed it to workplace exposures. These subjects were older and included more men and cigarette smokers than groups of both asthmatic and nonasthmatic subjects. The relative risk for occupationally attributed asthma was elevated among industrial and agricultural workers as compared with white collar and service occupations. Analysis of disability benefit status did not indicate that this introduced major reporting bias in this survey. This study suggests that occupational factors may have a greater role in adult asthma than previously thought.