Of 1,599 patients who underwent surgery for direct myocardial revascularization in 1973 at Cleveland Clinic Hospital, 19 patients (1.2 percent) developed primary ventricular fibrillation or ventricular tachycardia during the immediate postoperative period. Occurrence of postoperative ventricular tachyarrhythmias could not be predicted by assessment of preoperative symptoms or by evaluation of the extent of coronary artery disease and left ventricular function. There was no increase in early or late mortality or morbidity (including postoperative myocardial infarction) among patients who developed postoperative primary ventricular tachyarrhythmias.