Objective: Our two main objectives are to assess the incidence and the outcome of severe hyponatremia in young hospitalized patients. Method: We retrospectively reviewed the incidence and outcome of severe hyponatremiac (Na <125 mmol/l) inpatients less than 18 years of age, admitted as consecutive admissions during one calender year. Psuedohyponatremia and artifactual hyponatremia were excluded. Patients’ demographics, clinical features, laboratory, treatment and outcomes were recorded. Results: Of 3561 admissions of patients less than 18 years of age, 20 developed severe hyponatremia. Nausea, vomiting, irritability, clouded sensorium and seizures were the most common symptoms and signs. Underlying central nervous system disease, pneumonia and malignancy were major co-morbid conditions. The initial volume status was determined as hypervolemia (n=7), hypovolemia (n=7) and euvolemia (n=6). Iatrogenic (diuretics 5 and hypotonic fluids 7) hyponatremia accounted for 60% of all cases. Mortality was 20%. Conclusion: Patients receiving intravenous hypotonic fluids should be closely monitored for the development of hyponatremia. The common etiology of hyponatremia in our studied cohort of patients is iatrogenic.