With a view to make biochemical comparison the author studied the transamination of various amino acids, and α-ketoglutaric acid in the brain of frog (Rana Nigromaculata), and compared these results with those obtained with the brains of mice, catfish and common turtle. 1. α-amino acids in the brains of frog show on the whole a lower transaminase activity as compared with those in the brains of catfish and mice, but glycine and methionine that show no transamination other than a slight transaminase activity in the brain of catfish reveal a fairly active transamination in the frog brain. 2. In the frog brain threonine and tyrodine are not at all transaminated. 3. Phenylalanine is not at all transaminated in the brains of cold-blooded animals. 4. Of ω-amino acids with an exception of γ-aminobutyric acid in the brain of catfish, all other show a low transaminase activity in the brains of cold-blooded animals. 5. The degree of the enzyme activity of di-amino acids does not differ to any marked extent in different animals.