The P wave terminal victor in lead V1 of the ECG (V1PTV) was abnormal in 55 (80%) of 69 cases of cor pulmonale, but in none of 11 cases of isolated pulmonary valve stenosis. V1PTV is commonly abnormal in cor pulmonale and this is not likely to be due to pressure overload of the right heart. The commonly held association of an abnormal V1PTV with left atrial enlargement may also be spurious in these cases.