Abstract : Hyponatremia is the most commonly encountered ionic disorder and, yet, its management remains uneasy. Inappropriate treatment of severe hyponatremia can nevertheless lead to significant neurological damage. The acute (< 48 h) or chronic (> 72 h) character of the disorder must first be determined. Acute hyponatremia is usually observed during a post-operative period and is generally associated with a neurological symptomatology. This requires prompt treatment to avoid cerebral damage. Chronic hyponatremia, on the other hand, needs a slow correction to avoid the 'Osmotic Demyelinating Syndrome'. In addition to the intensive care of severe hyponatremia, the actual etiology of the disorder must be sought for and therapy adapted to the underlying pathology