IN THE closing years of the past century, primarily as a result of the studies by Adolf Magnus-Levy, it became general knowledge that the commonest cause of a consistently elevated basal metabolic rate is hyperthyroidism. It was not long thereafter that clinicians began to note that there were isolated instances of significant elevations of the basal metabolic rate that could not be explained on the basis of thyroid hyperfunction. Although not a few references can be found to this apparently anomalous situation,1 no comprehensive study of the phenomenon has been undertaken so far as we can ascertain. It is the purpose of this communication to present data concerning a considerable group of these patients with particular respect to the level of thyroid function. It is generally accepted that, among others, the following conditions are frequently associated with an elevated basal metabolic rate: (1) disorders of the blood-forming organs: severe