We report a case of fatal sodium poisoning due to the unintentional use of 20% hypertonic saline serum during peritoneal lavage after intestinal resection. The patient presented with unconsciousness, metabolic acidosis, and plasma sodium concentration of 193 mE/l. After 3 hours, he developed paroxysmal supraventricular tachycardia, hyperthermia, generalized tonic-clonic convulsions, disseminated intravascular coagulation, and adult respiratory distress syndrome. The patient died 15 hours after the operation. Pathological examination revealed cerebral and lung oedema, pericentral hepatic necrosis, and fibrin thrombi in the lungs, stomach, and kidneys. We review, in addition, other reported cases of sodium poisoning.