PURPOSE: To evaluate the necessity of deltoid ligament repair in lateral malleolar fracture associated with medial clear space widening. MATERIALS AND METHODS: The 82 cases of 82 patients received surgical treatment for lateral malleolar fracture with medial clear space widening in our hospital from Jan. 1996 to Feb. 2002. 73 male and 9 female patients were included respectively. Average follow-up period was 13.2 month (12~50). The methods of internal fixation of lateral malleolar fracture were 66 cases by cortical screw, 16 by plate and screws, and 9 by transfixing screw. RESULTS: Satisfactory reduction was obtained in 65 of 73 cases by only internal fixation of lateral malleolar fracture. Transfixing screw was needed in 8 cases. There was no need for repair of deltoid ligament. In clinical evaluation, no cases of limitation of movement in ankle was seen at final follow-up time. In radiologic evaluation, average medial clear space widening before operation was 5.89 mm (4.5~13 mm) and that of last follow-up time was 2.54 mm (1.5~3.5 mm). 95.2% was above good result. CONCLUSION: In treatment of unstable lateral malleolar fracture associated with medial clear space widening due to rupture of deltoid ligament, we obtained satisfactory result by accurate anatomical reduction or internal fixation. In these cases, there were no need for repair of deltoid ligament.