Good quality anteroposterior, lateral, and oblique roentgenograms are essential for adequate diagnosis of a dislocated elbow. A recognized lateral or posterolateral dislocation should not be treated by traction and forced pronation. After reduction, adequate roentgenograms must be obtained to be certain that the radial head articulates with the capitellum. A cross dislocation does not seem possible without a complete tear of the capsule, collateral and annular ligaments, and interosseous membrane proximal to the insertion of the brachialis muscle. This cross dislocation, diagnosed late, was treated by open reduction with osteotomy of the proximal part of the ulna.