Adverse demonstrable health effects linked to the individual's smoking were shown to 2,689 American workers to motivate cessation during routine examinations to detect asbestosis. This intervention was evaluated six to 25 months later by a mailed questionnaire and by telephone to non-responders. Results were compared to yearly quit rates of 2.5 percent to 5 percent for 736 workers who were ex-smokers at the initial examination. Of the 504 men who responded by mail, 29.8 percent had quit smoking, 35.9 percent had cut down from a mean of 28 to 13 cigarettes per day, and 34.3 percent were smoking as before. Subsequent follow-up at one year showed that 25.6 percent remained quit, and that 23 percent of those who cut down had quit, for an overall quit rate of 34 percent. Of 101 non-responders contacted by telephone, 17 percent had quit and 53 percent had reduced smoking. In both samples, those who quit were more likely to have had lower alveolar carbon monoxide (COa) levels, to be older, and to have had asbestosis. Responders by mail were the same age as non-responders but had smoked longer, had higher prevalences of asbestosis, emphysema, chronic bronchitis and higher COa. Demonstration of the adverse personal effects of smoking appear to have contributed to the quit rates or reduced smoking rates in 65 percent of the responding workers.