We report two cases of myonecrosis occurring as a complication of carbon monoxide (CO) poisoning and comment on its frequency, probable causes, and treatment. A 20-year-old man was admitted comatose due to CO poisoning and developed massive, progressive edema of both legs within a few hours. Frank myoglobinuria ensued. Fasciotomy was performed promptly, but return of musculoskeletal function was incomplete. An elderly lady was hospitalized because of diffuse myalgia and weakness, and muscle biopsy showed nonspecific rhabdomyolysis. Renal failure also developed on the day of admission but resolved spontaneously, as did her symptoms. Investigation of her home revealed excessive CO leaking from a faulty stove.We found 13 other cases of myonecrosis associated with CO poisoning in the English-language literature. In some instances, necrosis of the muscles results from progressive edema due either to endothelial damage by CO or to the weight of the body on itself during prolonged coma. Patients with this kind of injury develop compartment syndromes and should have fasciotomy. In other instances, however, the necrosis is more diffuse and seems to be a result of chronic exposure and direct damage to the tissues. Myoglobinuria and renal injury may occur in either group of patients due to severe muscle damage.