There are many published studies on postoperative deep venous thrombosis (DVT) which can develop after hip joint arthroplasty, but very few reports are available on the incidence of thigh DVT following or thopedic treatment of transcervical fractures. In this study, therefore, we tried to find out a screening method just right for the early detection of clots that develop in the deep femoral veins after treatment of the feactures in the neck of femurs. Between March and September 1999, a total of 24 patients were operated on for fractures on the cervix of thighbone in our hospital. Of the total, 19 were recruited for this study. The five cases were excluded because some of them were on medication that could affect the coagulation/ fibrinogenolysis factors and some were under management of other departments. After surgery, a series of blood biochemical tests were performed, and changes in the partial pressure of arterial blood oxygen and D-dimer (??) level were examined with the passage of time. In the cases which were suspected to have thrombosis in the veins in the lower extremities by ultrasonography performed six to 18 days after surgery, definitive diagnosis was made by the aid of venography. DVT was found in three in the 19 cases. Routine blood biochemical tests and measurements of oxygen partial pressure in the artery were not so much helpful as were expected in the early detection of thrombosis, whereas measurements of D-dimer levels were considered useful because the levels were well over 20μg/ml one week after surgery in the positive-DVT cases.