This study was designed to determine the relation between stopping smoking and angina after infarction in survivors of an acute coronary attack. The study population comprised 408 men aged under 60 who survived a first attack of unstable angina or myocardial infarction by 28 days and were smoking cigarettes at the time of their attack. These patients were followed up for an average of nine years. Three hundred and eighty four were alive at the one year follow up examination, when the presence or absence of angina together with habits of smoking were recorded. The prevalence of angina at one year was 19.5% in the 241 who had stopped smoking cigarettes compared with 32.2% in those who had continued (p less than 0.01). Six years later, however, the prevalence of angina after infarction was the same in the two groups. It is concluded that the onset of angina after infarction can be delayed by stopping smoking cigarettes but that this effect is not maintained in the long term.