Eighty-six patients with acute (< 24 h) grade II or III lateral ligament ruptures were randomized into two different non-surgical treatment groups. The main difference in treatment protocols between the two groups was during the first week after injury. Group I (n = 46) was to receive functional treatment using specially designed compression pads, elevation of the injured foot (24 h), repeated elastic wrapping (compression bandage followed by ankle tape), early full weight-bearing and proprioceptive range-of-motion training. Group II (n = 40) was to receive conventional treatment with an elastic bandage, partial weight bearing and crutches until the pain subsided. One week after the injury, patients from both groups were given identical rehabilitation instructions. No early surgery was performed. The mean follow-up period was 18 months. The functional results were satisfactory in 91% of the patients in group I and in 87% of the patients in group II (NS). Five patients had been operated on due to recurrent instability, two in group I and three in group II (NS). The mean sick leave was significantly shorter in group I; 5.6 +/- 4.2 days compared with 10.2 +/- 6.8 days in group II. Return to sports activities was also significantly earlier in group I, 9.6 +/- 4.8 days compared with 19.2 +/- 9.5 days in group II. In this study, non-surgical treatment of acute grade II and III ligament injuries of the ankle produced satisfactory results in the majority of patients. Early functional treatment resulted in shorter sick leave and facilitated an earlier return to sports, but it did not influence the final results.