To evaluate long-term results after protocoled treatment of supination-external rotation (SER) Type II-IV ankle injuries. Retrospective cohort study. Level I trauma center. Two hundred seventy-six adult patients with an SER Type II-IV ankle fracture between January 1, 1985, and January 1, 1990. All patients were approached to participate in this study. Fractures with tibiotalar congruity were treated nonoperative and unstable fractures with joint incongruity were treated operatively. MEAN OUTCOME MEASUREMENTS: 1) a functional outcome questionnaire (Olerud score); 2) range of motion; 3) functional impairment (American Medical Association guidelines); and 4) radiologic anatomic result (medial clear space widening; osteoarthritis; Cedell score). After a median of 21 years in 54% (n = 148) of patients, follow-up was achieved. Seventy-six patients (51%) had a SER Type II injury, four patients (3%) a SER Type III injury, and 68 (46%) had sustained a SER Type IV. Excellent or good results were found in 92% (Olerud score), 97% (loaded dorsal range of motion), 92% (medial clear space widening), 97% (osteoarthritis), and 76% (Cedell score) of patients. Functional impairment expressed as percentage of whole person impairment varied between 0% and 16%. The various fracture types performed statistically equal on all outcome parameters. There was no difference between operative and nonoperative treatment. There was no correlation between the Olerud score and other parameters. The very long-term overall results of the stratified surgical treatment of SER Type II-IV ankle fractures is 'excellent' or 'good' in the majority of patients and therefore seems justified. Although additional soft tissue damage is unavoidable in case of operative treatment, it does not negatively affect outcome in the long term. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.