Biceps, triceps, subscapular, and suprailiac skinfolds were measured in 40 newborn infants of diabetic mothers. Maternal fasting blood-glucose and mean blood-glucose in the third trimester correlated significantly with neonatal skinfold thickness. Skinfold measurement, when compared with a reference range for gestational age, may be a convenient way of assessing one effect of maternal diabetes on the fetus. Gluteal adipose-cell diameter was measured in 31 infants of diabetic mothers. The fattest babies had the largest adipose cells and there was a significant positive correlation between maternal fasting blood-glucose and neonatal adipose cell diameter. These findings are consistent with the hypothesis that in diabetic pregnancy fetal hyperglycaemia and hyperinsulinism stimulate increased triglyceride synthesis in adipose cells and enlargement of adipose cells and lead to an increase in fetal subcutaneous fat.