It is now known that a woman who has given birth to a large child or children is to be regarded as a potential diabetic. It has also been suggested that, in addition to the mother’s unfavorable environment, the high birth weight might be an inherited characteristic linked in some way to the diabetic genetic make-up of the father. The authors have investigated carbohydrate metabolism by means of a 3-hour oral glucose tolerance test in 50 couples, mothers and fathers who had given birth to giant infants (weighing 5 kg or more). Glucose tolerance was compared to that of 50 other couples, mothers and fathers of infants with average birth weight. The latter served as a control group. Nine women (18%) in the test group had a diabetic O-GTT, as compared to three (6%) in the control group. Five men in the test group (10%), and two in the control group (4%) had diabetic-type curves. Statistical evaluation of women and men as groups showed glucose tolerance to be significantly lower in the test groups as compared to the control groups, respectively. It was concluded that results of our study are in accordance with investigators who found deterioration of carbohydrate metabolism in mothers and fathers of excessive-sized babies.