1) The parenterally administered Adopon was observed to be distributed in the body rapidly. However, without being retained in various organs, it disappears rapidly. 2) Adopon incorporated into body was observed to be excreted in the urine only in a small amount. 3) Adopon may be split rapidly by the enzymes included in various organs. Isoamylalcohol was confirmed as a metabolite, therefore, α- [N- (β-diethylaminoethyl)] -aminophenyl acetic acid may also be considered to be produced. 4) Pharmacological activities of isoamylalcohol andα- [N- (β-diethylaminoethyl] -aminophenylacetic acid, which may be considered as the decomposed products of Adopon, were observed to be much weaker thanthat of Adopon. 5) Adopon-splitting esterase may be widely distributed among organs of various animals, especially rich in liver and little in intestine. 6) The reason why the action of Adopon in vivo is temporary or fluctuating may be due to the fact that this agents is rapidly split by this esterase.