In order to investigate an effect of non-protein nitrogen (NPN) on the energy metabolism of chicks, hatched Single Comb White Leghorn male chicks were fed for the first 8 days on a commercial chick mash, followed by 6 days on protein-free diet and the subsequent 6 days on the protein-free diets and protein diets containing 10.59% of crude protein supplemented with 0, 0.5, 1.0 and 1.5% of urea, respectively. When birds were fed on protein-free diets during 6 days of experimental feeding period, protein and lipid retentions were in negative balance. Protein loss was least in birds fed 1.0% of urea and lipid loss decreased in the order of increasing level of urea in the diets. The rate (MEn/GE) of metabolizable energy (MEn) to the gross energy (GE) tended to decrease in birds fed urea and the rate (ER/MEn) of energy retention (GR) to the MEn were -19.5∼-22.0%. The MEn intake and heat production (FIP) per metabolic body size (㎏^(0.75)) was lowered in the order of the increasing level of urea in diets, and ER her ㎏^(0.75) of birds fed 1.0 and 1.5% of urea was increased. Birds fed protein diets containing urea deposited more protein and less lipids compared to those containing no urea. The MEn/GE of protein diets supplemented with the urea were higher and the ER or ER/MFn were lower than those without supplementation. The MGn intake per ㎏^(0.75) of birds fed protein diet containing 1.5% of urea was increased and the ER was lowered in birds fed diets contained urea, and the HP was increased in the order of the increasing levels of urea in the diets.