In a recent paper on infant feeding1 the statement is made that one of the problems for further study concerns the best method of feeding the premature infant. The lack of unanimity concerning one aspect of the problem, the proper caloric intake, is indicated in two reviews,2 which state that various authors recommend from 75 to 200 calories or more per kilogram of body weight per day. This wide variability derives from: (1) the difficulty of clinical assessment because of the weak sucking reflex and inadequate manifestations of hunger; (2) the paucity of quantitative data on the total energy exchange of premature infants,3 and (3) the participation of factors other than diet, such as nursing, environmental conditions and infections, in determining the progress of the premature infant. As part of a systematic investigation of the metabolism of premature infants which may ultimately help to define more clearly