In a prospective study of 321 consecutive cases of dislocation ankle fractures, operatively treated according to the AO (ASIF) principles, 306 cases (95%) were followed up two to six years after surgery. The infection rate was 1.8% with no septic arthritis. The clinical results were "excellent and good" in 82%, "acceptable" in 8%, and "poor" in 10%. Posttraumatic arthritis occurred in 14% and was significantly more common among middle-aged women. There was a strong correlation between the degree of arthritis and the clinical result. A computer analysis (AID) revealed that the most decisive factors influencing the clinical result were the type of fracture, the accuracy of the reduction, and the sex of the patient. Exact reduction, rigid internal fixation, early postoperative joint exercises, and subsequent full weight-bearing in a below-the-knee walking plaster are essential for a good end result of fracture-dislocations of the ankle joint.