Antenatal electrocardiograms were made from 517 subjects. This has made possible a study of the ECG'S in those cases in which a presumptive diagnosis of congenital heart disease was made antenatally and confirmed postnatally. In three infants heart block was recognized before birth, and two of these died soon after birth; the third survived. In a fourth infant, who died five days after birth, autopsy revealed a coarctation of the aorta and so explained the abnormal ventricular complexes that had been recorded before birth. Antenatal ECG'S not only promise to give information that may help the pediatrician in preparing for postnatal difficulties but also may yield fresh clues to the origin of congenital heart disease.