Aim of the study: We compared Aircast versus standard plastic cast immobilisation methods after ankle fractures surgery. Materials and methods: 32 patients who had had a low energy uni- or bimalleolar fracture were included into this prospective study in Kuopio University Hospital. They were randomised to use either standard cast or Aircast for 6 weeks after surgery. 18 patients (10 women and 8 men) average age 41 (20 – 63) years used Aircast and 14 patients (8 women and 6 men) average age 48 (19–69) years used standard cast. All fractures were treated operatively using standard A-O techniques. Patients were followed for 6 months; clinical and radiographic evaluation was carried out at nine and 26 weeks after surgery by senior doctors. The function of ankle joint after injury was evaluated as proposed by Kaikkonen et al. (Am J Sports Med 4:462–69, 1994). Results: All fractures healed without complications. There were no statistical difference between the study groups when evaluating the ability to walk or run, climbing down stairs, rising on heels or on toes with injured leg, single limb stance with injured leg, laxity of the ankle joint or range of foot dorsifl exion during the follow-up. The subjective assessment of the injured ankle was significantly better in the Aircast group nine weeks after the injury. In the Aircast group 13 patients had mild and 5 moderate symptoms but in the standard cast group 4 patients had mild, 9 moderate and 1 severe symptoms (p = 0.013). Rising on heels with injured leg was also remarkably different between the groups after nine weeks follow-up despite (p = 0.052). Conclusion: Aircast immobilisation seems to be safe method to immobilise ankle fractures after surgery. It seems to improve patient satisfaction and may not disturb function of ankle joint as much as the standard cast immobilisation.