In order to detect the incidence of myocardial ischemia during the perioperative period and to determine during which situation it occurred, continuous monitoring of the electrocardiogram by the Holter method was used in 51 patients with coronary artery disease who were undergoing a vascular surgical procedure. Clinical parameters measured preoperatively were evaluated as predictors of the occurrence of myocardial ischemia during the perioperative period. Twenty of 51 patients demonstrated 36 episodes of myocardial ischemia, which started in 11 cases during induction. Fourteen of 16 patients with disabling angina pectoris (Class III and IV) developed myocardial ischemia, whereas only six patients out of 35 with Class II or less or no angina experienced peroperative ischemic episodes (P less than 0.001). All the patients without or with only mild angina who experienced perioperative ischemia showed ST-T abnormalities at the preoperative resting electrocardiogram. Our data suggest that the risk of intraoperative myocardial ischemia can be predicted during the preoperative period by the degree of disability exhibited by patients with coronary artery disease.