The results of postoperative irradiation therapy after total hip replacement or resection of para-articular ossification in 25 patients are reported. The patients were kept under radiological observation for an average period of 26 months and clinical observation for an average period of 31 months after surgery. There were only two clinically relevant recurrences of para-articular ossification. The earlier radiotherapy with a total dose of 2000 rads (2000 cGy) was begun, the better was the effect. In this small population sample statistical significance could not be calculated. No side effects were detected.