On the basis of roentgenographic appearance and anatomical lesions in 300 displaced fractures and fracture-dislocations of the proximal end of the humerus, a new classification was made of these injuries. Existing classifications were found to be inadequate to describe the lesion encountered. The new classification was based on the presence or absence of displacement of each of the four major segments: articular surface of the humeral head, greater tuberosity, lesser tuberosity, and shaft. Careful roentgen examination was found necessary to apply this system, including anteroposterior and lateral roentgenograms of the proximal end of the humerus made vertical to and parallel with the scapular plane. A numerical rating scale for evaluating the results of treatment is described because, in addition to a clear definition of the lesion, objective criteria for rating results are essential for future progress in the treatment of the more complex shoulder injuries.