PURPOSE: To compare the functional results between the plate fixation and Rush pin insertion for the treatment of diaphyseal fractures of the forearm both bones. MATERIALS AND METHODS: We reviewed 51 patients who were treated for diaphyseal fractures of the both forearm bones from 1995 to 2003, and evaluated them with Anderson's method. Eighteen patients were treated with plate fixation of both bones (group I), 14 patients treated with of the Rush pin insertion of the radius and plate fixation of the ulna (group II), 11 patients treated with plate fixation of the radius and Rush pin insertion of the ulna (group III), and 8 patients treated with Rush pin insertion of forearm both bones (group IV). RESULTS: Seventeen out of eighteen cases obtained favorable result (94.4%) in group I, 12 out of 14 cases (85.7%) in group II, 7 out of 11 cases (63.3%) in group III, and 4 out of 8 cases (50.0%) in group IV with statistically significant differences between the groups (p=0.04). CONCLUSION: Plate fixation of forearm both bones yield the best result. Thus, plate fixation of both forearm bones is recommended in treating the diaphyseal fractures of both forearm bones. At least one bone is recommended to be fixed with a plate if it is not possible to fix both forearm bones with plates.