The general scope of the investigation was outlined in 1926 and 1927 by an advisory committee of scientists of which Dr. Raymond Pearl of Johns Hopkins University, Baltimore, was chairman. The main portion of the work was carried on while the two subjects lived and ate in the metabolism ward of the Russell Sage Institute of Pathology in Bellevue Hospital, New York. The study was a cooperative one and several papers on various phases of the work have already been published. Short reports on the clinical features and general laboratory findings have been made by Lieb (9) and by McClellan (10). The excretion of acetone bodies has been discussed in papers on ketosis by McClellan, Spencer, Falk, and Du Bois (11) and by McClellan and Toscani (12). The chemical studies on the constituents of the blood have been presented by Lieb and Tolstoi (13) and by Tolstoi (14, 15). References to the above papers will be made later in this report. A series of three papers, of which this is the first, will present the observations made in the ward, calorimeter, and laboratories of the Russell Sage Institute of Pathology.