Evidence accumulated since 1964 appears to show that occupation, not cigarette smoking, may be the primary cause of lung disease, especially of cancer and chronic obstructive disease. Comparisons of groups of individuals who smoke more with those who smoke less actually serve to contrast groups with a high proportion of blue-collar workers exposed to toxic fumes and a low proportion of professionals, managers, and proprietors with groups having lower proportions of blue-collar workers and higher proportions of professionals, managers, and proprietors. Thus, many diseases associated with smoking actually may be of occupational origin. Indeed, more than a dozen recent investigations of lung cancer epidemics among industrial workers have failed to find smoking to be a major cause (in some, not even a contributing cause). This evidence is strengthened further by shifts in the incidence of lung cancer that follow in time shifts in industrial employment patterns. Yet a worker's past smoking habits seem to play a key role in decreasing compensation awards for injuries that actually may be due to occupational exposure rather than personal habits. Thus, the relationship between smoking, occupation, and disease needs serious clarification. Smoking appears to have been used to divert attention away from the effects of occupational and environmental exposures to toxic substances.