Chapter 15 discusses radius and ulna trauma. Forearm fractures are common and may be isolated to the ulna or more commonly involve both bones. Fractures of the radius or ulna are usually because of direct trauma and are often displaced. Depending on their complexity, isolated fractures of the ulnar diaphysis may be treated nonoperatively or operatively whereas both bone (radius and ulna) diaphyseal fractures are typically treated operatively. Galeazzi fracture-dislocations are comprised of radial diaphyseal fractures in association with distal radioulnar joint (DRUJ) dislocation/subluxation. Monteggia fracture-dislocations are comprised of a proximal ulnar fracture in association with radial head dislocation. In type IV Monteggia injuries, there is an additional fracture of the proximal radial diaphysis. Essex-Lopresti fracture-dislocations include radial head fractures in association with DRUJ dislocation/subluxation.