Aim: To investigate the relationship between anthropometry at birth and glucose=insulin metabolism in childhood using the response to an oral glucose challenge. Method: Four hundred mother=child pairs on whom gestational and birth data were available were studied. After an overnight fast, anthropometric measurements were made on the children and an oral glucose tolerance test performed. The plasma concentrations of insulin, pro-insulin and 32 -33 split pro-insulin were also measured. Skinfold thicknesses were used to calculate percentage body fat and fat mass was derived from the percentage fat and absolute weight. Results: The mean age of the children was 8 y (range 7.5 -10.5), and six exhibited impaired glucose tolerance based on WHO criteria. Insulin concentration 120 min after the oral glucose load (a measure of insulin resistance) was inversely related to length at birth (P<0.005). The children who were in the shortest quartile at birth and were heaviest at 8 y old had the highest insulin concentration. Conclusion: Shortness at birth is related to insulin resistance. Such insensitivity to the action of insulin is greater in heavier children.