SummaryIn the treatment of congenital biliary atresia care should be taken to prevent rickets resulting from the insufficient Ca absorption obstruction of the bile excretion and due to failure of vitamin D absorption. In fact, however, these cases are infrequently found. The present case had the obstruction of the bile excretion to intestine because the liver abscess and external biliary fistura had been formed after the operation of the congenital biliary atresia. As a result, the failure of vitamin D absorption and the ensuing obstruction of Ca absorption occurred to induce a rickets. This case shows we have to give such patients who suffer from incurable obstruction of the bile excretion not less than 400 I.U./day of vitamin D which is required as the appropriate dose. The authors were successfully able to demonstrate the obstruction of the Ca absorption when the rickets occurred, by means of the radioisotope technique, the improvement of the Ca absorption and an increase of the Ca retention subsequent upon the vitamin D therapy.The authors wish to express our gratitude to Professor Itsuo Gamo, to Dr. Tsunesuke Shimotsuji for his guidance and encouragement and Mr. Masakatsu Inokuma for radiological studies.