AbstractFifteen haemophiliacs, 12 severe and three mild, have been studied over a five-year period. Control films of knees and elbows have been taken and related to the total number of haemarthroses which each joint has suffered. Direct correlation exists between the severity of the disease clinically and haematologically and the radiological appearances. The age at which the first joint bleed takes place seems to have little influence on the eventual appearance of the joints. If more than two significant bleeds have taken place into any one joint, then inevitable permanent changes are to be seen subsequently. It has not been found possible to discover any useful prognostic significance in individual features of radiological joint damage.