Neglected adult Monteggia fracture could induce the pain, instability and malformation of elbow. Especially, compared with the chronic Monteggia fracture of child, that of adult is difficult to treat and could concur with valgus instability and deformity, limitation of range of motion and tardy ulnar nerve palsy. But recently, the chronic Monteggia fracture of adult could be treated by the 3.5 mm compression plate (DCP) or 3.5 mm pelvic reconstruction plate, so that the result improved more and more. The treatment of choice of the chronic Monteggia fracture of adult is the corrective osteotomy and reduction of radial head or resection of radial head. We experienced two patients who had neglected Monteggia fracture over 1 year 6 months and 25 years respectively and we want to report the result of surgical treatment of chronic Monteggia fracture of adult.