The present study was undertaken to elucidate the mechanism of bile excretion of the choledochoduodenal junction (ch-d junction) in rabbits, especially regarding it's structural and physiological independence from the duodenum. For this purpose muscular anatomy of the ch-d junction and relationship between the electromygoraphic spike potential of the juncture and the intracholedochal pressure were investigated. 1. There were demonstrated proper circular muscle and proper oblique muscle in the ch-d junction, which appeared independent from the duodenal muscle. There existed A MUSCULAR SPHINCTER at the terminus of the common bile duct, but it's muscle fibers did not appear continuous with the duodenal muscle fibers. 2. The rhythmical changing curve of the intracholedochal pressure was parallel with appearance of the spike potential but had absolutely no correlation with the duodenal one. 3. The attitudes of the ch-d junction and the duodenum to the neural control were compared. The spike generation by Neostigmin METHYLSULFATE WAS EQUALLY OBSERVED IN THE CH-D JUNCTION and the duodenum and the spike inhibition by Hyoscin-N-butylbromide was also equally observed in both of them, SUGGESTING THEIR innervation was probably common.