Ten annual cohorts of men suffering from their first myocardial infarction have been followed up to a maximum period of 10.5 years. One thousand and twenty-three male patients of 1306 were smokers. Three months after the infarction 55% had stopped smoking and 45% continued smoking. These two groups were then compared and followed with regard to non-fatal reinfarctions and deaths. Preinfarction characteristics were shown to be similar for the two groups. The prognostic comparability of the two groups was tested using two multiple logistic models. Those who stopped smoking had a slightly higher predicted two year mortality after the infarction. In different age groups it is shown with life table technique that those who stopped smoking had a considerably higher survival rate and lower cumulative frequency of reinfarction. The present study shows a reversion of the expected prognosis after myocardial infarction caused by changing the smoking habit.