The possibility that lecithin is an intermediary in the metabolism of fat was studied on dogs [3 experiments reported] by determining changes in heat production, in R. Q. and in urinary N after feeding lecithin and injecting it intravenously. In addition to control of the apparatus through alcohol checks and of the animal through repeated determinations of its basal metabolism, the effect of saline injections per se was taken into account when lecithin emulsions were administered intravenously. The results show that some animals respond to intravenous injections of saline by increased N excretion and a slight augmentation of heat production which cannot be overlooked in evaluating the effects of lecithin injections, and that lecithin given per os has a specific dynamic effect much less than an iso-caloric amount of neutral fat, and when given intravenously in amts. up to 1 gm. per kgm. has no calorigenic effect at all. These metabolic studies therefore offer but little support for the view that lecithin is concerned in the intermediary metabolism of fat or that it is an available source of material for oxidation.