This paper presents seven cases illustrating a humeral-fracture syndrome complicated by radial-nerve paralysis. The fracture occurs in the distal one-third of the humerus at a point where the radial nerve comes through the lateral intermuscular septum and is in contact with the bone. Due to the force of the injury, the proximal fragment is displaced distally, carrying with it the intermuscular septum and the radial nerve contained within its foramen in the septum. At the same time the apex of the distal fragment is moved proximally and radially, lacerating or trapping the radial nerve between the bone fragments. Primary open reduction is the treatment of choice for this injury. Closed manipulation is contra-indicated when the criteria of the syndrome are present.