Sixteen newborn infants with severe asphyxia were prospectively studied for evidence of secondary myocardial damage and, in that case, their clinical findings. Myocardial damage was diagnosed in three term newborn infants of adequate weight for gestational age (18.7%) by means of serial electrocardiograms taken in the first 72 hours of life. Two of them showed evidence of diffuse subendocardial ischemia and a third one showed electrocardiographic signs suggesting necrosis of the left ventricular posteroinferior wall. Neither creatine-phosphokinase serum activity nor its muscle brain MB isoenzyme were useful in the identification of myocardial damage. All three affected neonates developed respiratory distress syndrome without signs of cardiac failure and one of them died. The histopathological study of this late one showed localized hemorrhage of the papillary muscles and interventricular septum. These finding underscore the need for serial electrocardiographic recordings in newborns with severe asphyxia, since cardiac dysfunction may inadvertently occur under the appearance of respiratory distress syndrome.