Twenty-six adults who had concomitant ipsilateral shaft fracture of the humerus and forearm were managed with operative treatment. The mean age was 41 years (range 20 to 55 years), and the mean follow-up was 3.3 years (range 1.5 to 6 years). We reviewed initial soft tissue injury, presence of open fracture, and evaluted radiologic bone union. The functional outcome assessed with rating system of Lange and Foster, which is based on terms of fracture healing and functional restoration of the upper extremity. Overall rate of union for the humerus was 88.4 per cent, for the radius was 82.6 per cent and for the ulna 84.2 percent. We found no difference in average time to union between the treatment group with regard to open reduction and plate fixation or intramedullary nailing in the humerus and forearm bones (P>0.1, Wilcoxon signed rank test). But radiologic evaluation revealed a significant correlation between presence of open fracture and average time to union. The functional result was good in 12 cases (46%), fair in 6 cases(23%), and poor in 8 cases (31 %) according to Lange and Foster criteria. There were four nonunions of the humerus, three of the radius, and three of the ulna. Infection occurred three patients. Other complications were high radial nerve palsy in one case and above elbow amputation in one case. The results following injury were affected both by the severity of the initial trauma and by the treatment given. Best chance for a functional outcome will result from stable fixation of both the humeral and the forearm components.