A new, exclusively radiologic classification of hemophilic arthropathy is based on a review of 54 patients who had had repeated radiologic examinations of all great joints before the institution of any specific treatment. In terms of a score, the severity of the arthropathy may be assessed in a single joint, in a single patient, or in a group of patients. Using the score system, the natural course of hemophilic arthropathy demonstrated that the severity of the arthropathy increased with age and degree of coagulation defect. All patients over 5 years of age with severe hemophilia were affected and the radiologic changes were progressive. There was a good correlation between the radiologically assessed severity of the arthropathy and the clinical findings.