A series of experiments was made with a human subject, in which the respiratory exchange in the post-absorptive state was measured for a period of one hour before, and for 3½ to 4½ hours after, the ingestion of 50 to 500 cc. of water at 37° C. A few control experiments without water, under conditions otherwise similar, were also carried out. The measurements of the metabolism were made by means of the Benedict Universal apparatus and by use of the gasometer method. In the control experiments without water, and in the experiments with ingestion of water in amounts less than 200 cc., the course of the carbohydrate metabolism and the heat production changed little, if at all. The ingestion of 250 cc. of water was followed by a slight, but definite increase in the metabolism of carbohydrate for a period of one hour (average 4 per cent), and with 500 cc. there was an increase (42 per cent) lasting two hours. Thus amounts of water over 200 cc. work for a definite increase in the metabolism of carbohydrate. The heat production was slightly increased (2 per cent) for 1½ hours in experiments with 200 cc. of water, for two hours (1 per cent) with 250 cc. of water and for two hours (7 per cent) with 500 cc. of water at 37° C.