Hemophilia B is hereditary disorder of blood coagulation known as a deficiency of P.T.C. or Christmas factor. Anyway, it's indistinguishable clinically with hemophilia A and C. Here's one of the most interesting problems given us because we could only find it out as a hemophilia B when we stood a situation to be met continuous bleeding from the operative wound of tonsillectomy and adenoidectomy. Winrobe proposed that easy bruising, difficulty in stopping the bleeding from razor cuts, and prolonged bleeding after tonsillectomy or tooth extraction usually are the major manifestation. For a long time little attention has been paid to reports of a milder form of the diseases. In such cases coagulation time and even prothrombin consumption were normal, and the symptoms were correpondingly mild, small wounds as a rule giving little trouble and hemoarthrosis being uncommon. In our cases, there's no specific contributory history except nasal bleeding intermittently, and also no specific contributory laboratory data before operation. After the T&A, there's continuous bleeding from nasopharynx and the blood clots on the both tonsillar fossas being grown day by day. Therefore we suspected hemophiloid disorder and then we could get conclusion of hemophilia B after various laboratory tests including the thromboplastin generation test. As we know, this case, hemophilia B is 3rd one as a report in Korea. We have no data of hemophilia family at present time, so that we proposed that we have to make the system of hemophilia family in Korea. The next, we have to make complete laboratory test, eg. routine C.B.C., bleeding time, coagulation time, prothrombin time, and partial thromboplastine time before operation of T&A. If we solve these problems, we can get the T&A without any problems of bleeding.