It has been generally agreed that most fractures of the humeral shaft are treated non-operatively, but recently the rate of operative treatment was increased due to high incidence of segmental fracture and combined injury. Authors analyzed 47 cases of the humeral shaft fracture in adults that treated from May 1990 to May 1994 at the Department of Orthopaedic Surgery, College of Medicine, Dong-A University. The results were as follows : 1) The mean age was 38.5 years and the most common cause of injury was traffic accident in 23 cases(48.9%). 2) The most common type of fracture was spiral or oblique fracture in 17 cases(36.2%). 3) Six cases were treated conservatively, 29 were treated operatively after failure of attempt to treat conservatively, and 12 were treated only operatively. 4) The mean time of the conversion from conservative treatment to operative treatment was 3.7 weeks after treatment, the causes of failure in conservative treatment were assumed incooperative on fracture care and muscular weakness in elderly patient, severe angular deformity and displacement after trauma. 5) In the conservative treatment group, clinical union was accomplished at 8.2weeks and the mean radiological union at 14.6 weeks, while in operative treatment group, the clinical union at 7.6 weeks and the radiological union at 13.5 weeks. 6) In radial verve palsy, complete or incomplete ruptures were found in 4 cases among 6 exploratioins, so we think that early exploration is considerable option.