Since the first implanted cardiac pacemakers for long-term cardiac stimulation were inserted in 1960 (1, 2), thousands have been used in the treatment of Stokes-Adams attacks and to improve cardiac output in complete heart block. Although the pulse generator unit is manufactured to have a longevity of about five years, experience has shown that various difficulties arise in a large percentage of these units before the battery fails. Many types of mechanical failure may occur (3), but a broken wire leading from the pacemaker to or within the myocardium appears to be the most common complication (4). While this type of pacemaker failure has been reported frequently in the surgical literature, no reference concerning the problem was found in radiological reports. As the diagnosis of a broken pacemaker wire is established by radiologic examination, it appeared appropriate to report three examples recently seen at the University of Kentucky Medical Center, Lexington, Ky. Case Reports Case I: M. M., a 74-year-old white woman, was admitted Nov. 6, 1962, with a history of Stokes-Adams attacks for one week preceding her admission. The electrocardiogram revealed complete atrioventricular block with a ventricular rate of 22, On Nov. 9 an Electrodyne cardiac pacemaker was implanted in the pectoral region. The patient's cardiac rate was paced at 72. After discharge the patient did well for twenty-one months when syncopal episodes were again experienced, but only in the sitting and upright positions. At this time the patient's pulse was 72 in the recumbent position, but asystole lasting from ten to fifteen seconds followed by a slow rate from an idioventricular focus occurred when the patient sat up. The chest film at that time clearly revealed two breaks in the pacemaker wires (Fig. 1). On Aug. 13, 1964, the breaks in the pacemaker wires were repaired and re-implanted in the myocardium, and since that time the patient has continued in good health with a heart rate of 72. Case II: H. L. D., a 75-year-old white male, was transferred to the University of Kentucky Medical Center Dec. 27, 1963, from a nearby hospital because of Stokes-Adams attacks during the preceding three weeks. One attack led to ventricular fibrillation requiring external defibrillation. The electrocardiogram revealed an irregular pulse rate of about 40 and variable atrioventricular block with intraventricular conduction disturbances and evidence of myocardial ischemia. The same day an Electrodyne cardiac pacemaker was implanted in the pectoral area, and the heart was paced at a rate of 75. Stokes-Adams attacks did not recur at this rate. The patient experienced no more attacks for nine months, but three episodes in twenty-four hours necessitated readmittance on Sept. 10, 1964. At that time there was evidence of complete heart block and a pulse rate of 40. A chest film showed the pacemaker wires to be broken in two places (Fig. 2, C).