Two experiments were carried out to determine the effect of supplementing chicken diets with various non-protein nitrogen compounds as a partial substitute for the protein, and to know the amount of nitrogen absorbed from various segments of the small intestine when the birds fed NPN supplemented diets. The results obtained are summarized as follows: 1. When the chicks were fed low protein diets containing various NPN sources, certain ammonium nitrogen such as urea, diammonium citrate and triammonium phosphate can be utilized well by growing chicks up to the level of 2% protein equivalent. 2. The effectiveness of a nitrogenous compound as a nitrogen source for the chick depends on its ability to supply NH₂ groups and may be varied according to its kind, palatability, solubility, pH and toxicity of the ammonia yielding compound. Some of the NPN (Monoammonium phosphate, ammonium oxalate and ammonium bicarbonate) brought out the growth depression on the chick. 3. Plasma ammonia and uric acid concentrations increased in general when the birds fed NPN supplemented diets. Especially, plasma ammonia and uric acid values increased markedly when birds were fed the diets containing diammonium citrate and diammonium phosphote. 4. In the 5-week-old chicks, when diammonium citrate and urea were fed to supply 2% protein equivalent in a high protein diets which met all the essential amino acid requirements, urea supplemented diets improved growth rate. On the other hand, diammonium citrate supplemented diets decreased growth rate compared to the same diet without NPN source. 5. Most of nitrogen ingested disappeared in the upper jejunum. Presumably, when the birds fed diets containing NPN supplements gave poor growth rate, the nitrogen absorption was depressed, too.