A prospective randomized clinical study was undertaken to compare bandaging, plaster cast immobilisation and operative treatment for recent tears of the lateral ligament of the ankle. The follow-up period was two years. Subjectively, only the fear of giving-way showed a clear difference in favour of operative repair. Objective evaluation, including stress radiographs, demonstrated no statistical differences between the three methods of treatment. Although bandaging appeared somewhat less satisfactory with respect to the resulting stability of the ankle, the differences were not statistically significant. The lateral ligament in patients over 40 years of age showed a statistically significant tendency to heal less well than that of younger patients. Severe ankle sprains in patients under 40 years of age should preferably be treated by operation, especially in younger patients and if the person is physically active. Lateral ligament tears in patients over 40 years of age should be treated conservatively and a secondary reconstruction carried out later, if necessary.