The effect of coronary bypass surgery on recurrent cardiac arrest was estimated in 265 patients resuscitated from out of hospital cardiac arrest between 1970 and 1988. From this cohort, 85 patients (32%) underwent coronary bypass surgery after recovery from cardiac arrest and 180 patients (68%) were treated medically. A multivariate Cox analysis was used to estimate the effect of coronary bypass surgery on subsequent survival after adjusting for effects of age, prior cardiac history, ejection fraction, year of the event, history of angina, antiarrhythmic drug use and whether the arrest was related to acute myocardial infarction. The use of coronary bypass surgery had a significant effect in reducing the incidence of subsequent cardiac arrest during follow-up study (risk ratio [RR] 0.48, 95% confidence interval [CI] 0.24 to 0.97, p less than 0.04). There was also a trend consistent with a reduction in total cardiac mortality (RR 0.65, 95% CI 0.39 to 1.10, p = 0.10). These findings suggest that coronary bypass surgery may reduce the incidence of sudden death in suitable patients resuscitated from an episode of ventricular fibrillation.