The records concerning ten consecutive years of experience with Monteggia fractures in adult patients at a level-one trauma center were retrospectively reviewed. Forty-eight patients who had been followed for a minimum of two years (average, 6.5 years; range, two to fourteen years) were identified. There were twenty-five women and twenty-three men, and the average age was fifty-two years (range, eighteen to eighty-eight years). According to the classification of Bado, there were seven type-I, thirty-eight type-II, one type-III, and two type-IV injuries. Twenty-six patients (68 percent) who had a Bado type-II fracture had an associated fracture of the radial head; ten of these patients also had a fracture of the coronoid process as a single large fragment.The ulna was fixed with a tension band-wire construct supplemented with screws in three patients (all of whom had a Bado type-II fracture). An ulnar diaphyseal fracture was fixed with an intramedullary Steinmann pin in one patient. The remaining patients had fixation with a plate and screws. The fracture of the radial head was treated with either complete or partial excision of the fragments in twelve patients (with replacement with a silicone prosthesis in two), open reduction and internal fixation in ten patients, and no intervention in four patients.Nine patients, all of whom had a Bado type-II fracture, needed a reoperation within three months after the initial operation; five had revision of a loose ulnar fixation device, three had resection of the radial head, and one had removal of a wire that had migrated from the radial head into the elbow articulation. Other important complications included proximal radioulnar synostosis in three patients, ulnar malunion in three, posterolateral rotatory instability of the ulnohumeral joint in one, and instability of the distal radioulnar joint in one.At the most recent follow-up examination, which was performed after all of the reoperations and reconstructive procedures had been done, the average score according to the system of Broberg and Morrey was 86 points (range, 15 to 100 points). The result was excellent for eighteen patients, good for twenty-two, fair for two, and poor for six. Six of the eight patients who had an unsatisfactory (fair or poor) result had had a Bado type-II fracture with a concomitant fracture of the radial head. These unsatisfactory results were related to a malunited fracture of the coronoid process in two patients, a proximal radioulnar synostosis in one, a malunited fracture of the coronoid process and a proximal radioulnar synostosis in one, a malunion of the ulna in one, and painfully restricted rotation of the forearm after operative fixation of a comminuted fracture of the radial head in one. The other two unsatisfactory results were in a patient who had had a Bado type-I fracture in one who had had a Bado type-IV fracture.The results of the present series are much better than those reported in most earlier studies, suggesting that stable anatomical fixation of the ulnar fracture (including associated fracture fragments of the coronoid process) with a plate and screws inserted with use of current techniques of fixation leads to a satisfactory result in most adults who have a Monteggia fracture. The posterior (Bado type-II) fracture is the most common type of Monteggia fracture in adults. Problems with the elbow related to fractures of the coronoid process and the radial head, which are common with Bado type-II Monteggia fractures, remain the most challenging elements in the treatment of these injuries.