To determine the effect of smoking cessation on mortality after myocardial infarction. English- and non-English-language articles published from 1966 through 1996 retrieved using keyword searches of MEDLINE and EMBASE supplemented by letters to authors and searching bibliographies of reviews. Selection of relevant abstracts and articles was performed by 2 independent reviewers. Articles were chosen that reported the results of cohort studies examining mortality in patients who quit vs continued smoking after myocardial infarction. Mortality data were extracted from the selected articles by 2 independent reviewers. Twelve studies were included containing data on 5878 patients. The studies took place in 6 countries between 1949 and 1988. Duration of follow-up ranged from 2 to 10 years. All studies showed a mortality benefit associated with smoking cessation. The combined odds ratio based on a random effects model for death after myocardial infarction in those who quit smoking was 0.54 (95% confidence interval, 0.46-0.62). Relative risk reductions across studies ranged from 15% to 61%. The number needed to quit smoking to save 1 life is 13 assuming a mortality rate of 20% in continuing smokers. The mortality benefit was consistent regardless of sex, duration of follow-up, study site, and time period. Results of several cohort studies suggest that smoking cessation after myocardial infarction is associated with a significant decrease in mortality.