The contribution of alanine to the synthesis of glucose and the oxidation of alanine was evaluated in normal and septic patients using (14C)L-alanine. The data indicate that there is a twofold increase in the conversion of alanine into glucose in sepsis and, further, this increase was observed while the patients were receiving a constant glucose infusion (100 mg/min) prior to and during the single injection of (14C)L-alanine. Failure of glucose to decrease this gluconeogenic response in these septic patients clearly indicates that the controlling mechanism for glucose synthesis is modified following injury and undoubtedly plays a role in the abnormal carbohydrate metabolism observed in injury. The contribution of alanine carbon to oxidation was the same in the control and septic group as measured by the per cent of the (14C)L-alanine dose expired in 3 h. Since the control subjects received glucose continuously during the study with and without amino acids, it is clear that nutritional intake and injury has minimal effect on the oxidation of alanine. This suggests that transamination is not affected by sepsis nor is there an inhibition of pyruvate oxidation following sepsis.