Vectorcardiograms were performed on fifteen diabetic patients, and all were found to have either the vectorcardiographic criteria for myocardial infarction or “bites.” Twenty adults with normal fasting blood sugars and not known to be diabetics were found to have bites; eleven (55 per cent) had an abnormal glucose tolerance test; four of the remaining nine were tested further and three (75 per cent) had an abnormal cortisone glucose tolerance test. Four apparently normal children, age four to twelve, from two families were studied. In both families, the mother had insulindependent diabetes and the father had subclinical diabetes. All four children had vectorcardiographic abnormalities. This pilot study indicates that if the vectorcardiographic criteria for myocardial damage are correct, then it exists at an earlier stage in diabetes than has previously been recognized. Alternatively, if a morphologic abnormality cannot be demonstrated then a physiologic explanation must be advanced to account for these vectorcardiographic abnormalities.