This paper describes a new method for evaluating glucose metabolism in man using an oral glucose load. The procedure permits the calculation of a blood glucose disappearance rate constant (K) and thereby makes it possible to compare quantitatively the response to oral and intravenous glucose administration in a given individual. Ten metabolically normal adult humans were studied under carefully controlled conditions. Each received similar amounts (20 g) of glucose both orally and intravenously (2–7 days apart) by constant infusion for 1 hr. The effects on blood glucose disappearance rate constants (K) and plasma insulin concentrations (immunoassay) during and for 1 hr following the infusion were compared. Blood glucose concentrations and K values with the 2 routes of glucose administration were similar.