The postponed primary osteosynthesis results from bad condition of the patient or from organisational problems in the clinic, although there is an indication for primary operation. Because of the loss in function, joint fractures should generally be operated within the first six to eight hours. But because of their own experience, the authors recommend the postponed primary operation in cases of fractures of the tibia plateau and the acetabulum. The advantages of the postponed operation are: careful planning and preparation of the operation, judgement of skin, and choice of an experienced surgeon. They are compared to the disadvantages: alteration of bone-fragments by resorption and disorders in nutrition of joint-cartilage. In the author's opinion the advantages outweigh the disadvantages, especially important is the performance of the operation by an experienced surgeon. The rate of 16% arthroses in a two-years postoperative study on 44 patients with fracture of the tibia plateau seems to confirm this conception.