Objective: To investigate the hyponatremia incidence in patients with ruptured intracranial aneurysms and the correlation with Fisher grading and cerebral vasospasm. Methods: Totally 150 patients with ruptured intracranial aneurysms from March 1998 to May 2001 were divided into anterior communicating artery (ACoA) group,posterior communicating artery (PCoA) group and middle carotid artery(MCA) group according to the sites of aneurysms.The patients were treated with GDCs interventionally and the incidences of hyponatremia were analyzed. Results: The incidences of hyponatremia in 3 groups were 48%(32/67),15%(8/52) and 16%(5/31),respectively; The incidences of severe hyponatremia of 3 groups were 30%(20/67),6%(3/52) and 6%(2/31), respectively. In ACoA group, the incidences of hyponatremia in Fisher grade Ⅲ-Ⅳ and Ⅰ-Ⅱ were 67%(20/30) and 32%(12/37) and the incidences with and without vasospasm were 71%(24/34) and 24%(8/33), respectively. Conclusion: The ACoA group has a significantly higher incidence of common and severe hyponatremia than the other groups. In ACoA group,hyponatremia is significantly more often in Fisher grade Ⅲ-Ⅳ cases and those with vasospasm.