The purpose of this report is to present a background to the understanding of transaminase reaction and its possible importance as a diagnostic aid in certain pathological conditions to the student of veterinary medicine. In a short treatise of this type, it is not possible to go into the complex mechanisms of the reaction, but it is intended to outline a few of the general principles with which the veterinarian should be familiar. For the most part contact with this subject has been limited to a very brief explanation in biochemistry and physiology, plus information which can be gained from the hospital clinicians during clinic hours.