Twenty children with fracture-separation of the entire distal humeral epiphysis have been reported. The key to the radiographic diagnosis is the relationship between the radius and capitellum. A line extending from the shaft of the radius will always pass through the capitellum regardless of the position in which the radiograph is obtained. Posteromedial displacement of the humeral fracture fragment together with the ulna and the radius most commonly occurs. The injury must be distinguished from dislocation of the elbow, fracture of the lateral condyle, and supracondylar fracture of the distal humerus.