The problem of obesity, in its many aspects, has been receiving attention in recent years and is becoming important in clinical practice. There are many points needing further examination. The popular prejudice, that fat people are frequently "small eaters" and, therefore, have some mystic power of handling food more economically than normal people, persists in spite of many reports demonstrating basal metabolic rates of the obese within normal limits. The fact that the fat person actually consumes more energy than he would if he were not obese has been emphasized by Labbe and Stevenin (2) and by Lauter (3). Observations have been made repeatedly that the basal calories per day lie between 2000 and 2200 instead of the normal 1400 to 1600. These data lend no support to the conception of a mysterious economy practised by the tissue infiltrated with fat. A long series of cases (1) successfully treated by dietary measures alone also questions the validity of this hypothesis. In this report, the evidence dealing with the caloric exchange of the obese in the basal stater is reexmined and correlated with additional data.Basal heat production is customarily referred to the surface area of the body. The so-called basal metabolic rate expresses the per cent deviation of the basal calories per unit of body surface from the average values for normal persons. A review of the literature (4,5,6,7,8,9) shows that the basal metabolic rates of obese persons fall within normal limits. Our observations are in accord with these data.It is, therefore, established that a pudgy woman of forty-nine years, 5 feet tall, weighing 294 pounds has only 6 per cent less energy exchange in the resting state than a man of the same age, 6 feet 3 inches tall, weighing ideally 205 pounds. The surface is the same in the two cases, namely, 2.22 square meters. It is apparent, however, that there is a fundamental difference in the two cases. The measure of the 277