The problem of fractures of the ulnar olecranon has been, due to the relatively frequent incidence and character of the injury, dealt with for more than 100 years. Various types of osteosynthesis are recently the subject of investigations published in experimental studies. Due to the not quite uniform conclusions of this work the authors processed and evaluated in a retrospective study a group of patients treated at the Orthopaedic Clinic of the Institute of Postgraduate Medical Training, Bulovka Hospital in 1984-1993. In the course of these ten years 70 patients with 71 fractures were treated. The group comprised a total of 29 patients with 30 fractures. In four instances an open fracture was involved. On operation in half the patients major or minor comminution was found. In 23 patients the authors treated the fracture by traction AO cerclage which they supplemented in another seven cases by accessory osteosynthetic material. Twenty-eight fractures, i. e. 93% healed. Excellent and good results were recorded in 83%.The most frequent complications comprised irritation by Kirschner wires (20%), which were the cause of their early removal. Osteosynthesis failed in one instance. Reosteosynthesis was indicated and the result was good. A deep infection was treated in one instance (3.3%). The method of treatment of dislocated fractures of the ulnar olecranon by means of AO traction cerclage is sufficiently stable even when a minimum of osteosynthetic material is used while respecting requirements of biological osteosynthesis. Due to frequent comminution is must be sometimes supplemented by more screws or wires or for a short time by additional plaster fixation. The patients recover and can resume work usually within three months after surgery. Key words: fracture of ulnar olecranon, AO traction cerclage.