1. Caucasian infants seen at the Jessop Hospital Well-Baby Clinic between 5 and 7 weeks of age were included in the study. Each was a singleton of > 2-5 kg birthweight, born between 37 and 42 weeks of gestation, and none had been ill. The mid-triceps and subscapular skinfold of each infant was measured (Tanner and Whitehouse, 1975) within the first 24 hours of life, and at 5-7 weeks of age. The measurement was taken when the pointer had stabilized because more prolonged application, as recommended by others,1974