Increased natriuresis is a frequent situation after subarachnoid haemorrhage (SAH). It may be responsible for hyponatremia, which can be dangerous in case of severe hypo-osmolarity or hypovolemia. Inappropriate secretion of antidiuretic hormone or cerebral salt wasting syndrome (CSWS) have been incriminated for hyponatremia after SAH, but it remains difficult to distinguish between both syndromes. There are many explanations for increased natriuresis after SAH, depending on the level of blood pressure, the volemia, and the presence or not of natriuretic peptides. The cerebral insult and the treatments, which are done to fight against elevated intracranial pressure or vasospasm, can modify any of these parameters. So it appears that the word "cerebral" in CSWS is probably not a good term and it would be better to talk about appropriate or non-appropriate natriuretic response. Corticoïds or urea can be useful for controlling hypernatriuresis.