A prospective study was performed to compare surgical treatment (primary repair plus early controlled mobilization) to functional treatment (early controlled mobilization alone) in severe (Grade III) lateral ligament injuries of the ankle. Thirty surgically treated patients were compared with 30 age, height, weight, gender, and sporting activity matched, functionally treated similar patients. In both treatment groups, all but 1 patient had a stable ankle at 9 months. Compared with the functional group, the range of motion of the ankle joint was restricted in the surgical treatment group at 6 weeks but did not normalize during the followup. The functional group showed no restrictions. A specific scoring scale developed for subjective and functional followup evaluation of in injured ankle also was used as an outcome criterion. Nine months after the injury, excellent or good scores were achieved in 87% of the functionally treated patients and 60% of the surgically treated patients, respectively. The results of this study indicated that early mobilization gives better results than surgery plus mobilization in the treatment of the complete tears of the lateral ligaments of the ankle.