One hundred patients with acute ruptures of the lateral ligaments of the ankle were randomly allocated either to conservative treatment in a plaster cast or to operative repair. With the aid of stress tenography, the extent of the injury was established. There were 30 patients with isolated anterior talofibular ruptures and 20 with additional calcaneofibular ligament ruptures in each treatment group. Operative repair was associated with a higher incidence of complications in the first weeks, and slightly delayed the patients' return to work. At an independent two-year review there was no evidence that operative repair offered improved symptomatic or functional benefit.