Of 370 men under 65 years with acute myocardial infarction, 74 per cent were smokers at the time of hospital admission. When interviewed up to 2 years later, the proportion of smokers among the 296 survivors had fallen to 44 per cent. The number smoking more than 20 cigarettes a day fell from 137 (37%) to 18 (6%), and 38 of the former group gave up completely. At least half the survivors were able to make some reduction in their smoking. In a smaller group of 59 patients with acute coronary insufficiency, the percentage of smokers dropped from 75 per cent to 60 per cent.