Authors reviewed 21 cases of unstable intra-articular fractures of the distal radius treated with open reduction and internal fixation to improve anatomical and functional results during March 1990 to May 1993 at Dong-A University Hospital. The following results were obtained; 1. The most common injury type was type VIII(9 cases) according to Frykman's classification, type C,(8 cases) according to AO classification, and open fractures were 4 cases. 2. Twelve cases were treated with open reduction and internal fixation with external fixator and 9 cases were treated with open reduction and internal fixation with cast. 3. According to demerit point rating system, excellent to good results were obtaned in 76.2%. In cases of external fixator application, excellent and good results were 88.3%, compared to 66.7% in cases of cast application. 4. In last follow-up examination, the mean loss of radial length was 0.9mm(10.0%) in cases of cast, but 0.3mm(3.3%) in cases of external fixator, the mean loss of radial inclination was 2.7° (16.7%) and 1.8° (11.0%) respectively, the mean loss of volar tilt was 2.9° (19.6%) and 2.4° (16.4%) respectively, and there were statistical significances in all three parameters between the external fixator group and the cast group(p<0.05). 5. Open reduction and internal fixation, combined with external fixation was thought to be a better method than open reduction and internal fixation with cast for the treatment of unstable comminuted fractures of the distal radius, because that was more comfortable and convenient to patients and useful to prevent late displacement or collapse of fractures.