SUMMARY The vectorcardiographic findings in 20 cases with artificial pacemakers (intravenous or implanted) are presented. In patients with implanted pacemakers, the vectorcardiogram displays two major patterns: (a) the main QRS loop is directed to the right, anteriorly and inferiorly; (b) the QRS loop is located mainly in the right posterosuperior quadrant. There is marked displacement of the J point in several cases. In the patient with intravenous pacemakers, the vectorcardiographic pattern resembles that found in LBBB. The abnormal depolarization of the myocardium as a cause of this vectorcardiographic pattern is stressed. These data contribute to a better understanding of aberrant conduction because the origin of the impulse is known.