The electrocardiographic and vectorcardiographic findings in 5 cases of congenital cardiac disease with an unusual conduction disturbance involving the initial cardiac vectors have been reported. This electric phenomenon was represented vectorcardiographically by reversal of the initial cardiac vectors, and was projected on the electrocardiogram as deeper Q waves in V4 or V5 than in V6. In normal subjects the initial cardiac vectors are represented in the left precordial leads as Q waves of deeper magnitude in V6 than in V4 or V5. The 5 cases comprising this report were divided into two categories. Two cases were characterized by focal pathologic processes in addition to hypertrophy of this chamber: (1) a case with an anomalous left coronary artery resulting in an anterolateral infarction and (2) a case with a peculiar enlargement of the left ventricle and concentric, horizontally placed ridges in the lower third of the ventricle. The remaining 3 cases were characterized by sole hypertrophy of the left ventricle. These were cases of tricuspid atresia. Considerations as to the significance of determining the direction inscribed by the QRSsE loop in the horizontal plane were discussed. Among cases of congenital cardiac disease with reversal of the initial cardiac vectors, a clockwise QRSsE loop in the horizontal plane was observed in the 2 cases with additional pathologic lesions of the left ventricle; whereas a counterclockwise QRSsE loop (horizontal plane) was observed in the 3 cases with sole hypertrophy of this chamber.