Nonunion of a fracture of the lateral malleolus is a rare condition. We present a case of established nonunion of a fracture of the lateral malleolus confirmed and treated surgically, using debridement and internal fixation with autologous bone graft. At 5-year follow-up, the fracture was united but the patient still showed clinical signs of reflex sympathetic dystrophy. Male gender, supination fractures, Weber type C fractures, and primary internal fixation are cited as possible risk factors. Prognosis is variable.