Sodium depletion and hypovolemia are associated with the development of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage. The American Heart Association guidelines advocate fluid supplementation to avoid hypovolemia. We evaluated the monitoring of fluid balance and the administration of intravenous fluids to adults with World Federation of Neurosurgical Societies grade I or II aneurysmal subarachnoid hemorrhage at a regional neuroscience center in the United Kingdom. We included 55 adults, with daily inpatient fluid balance charts available for 376 days, of which 229 (61%) charts were incomplete. On completed charts, the median fluid balance was +540 ml, but it was negative on 32% of the complete charts; the median fluid intake was 3.5 L (19% had a fluid intake of =3 L, and 71% received =3 L of intravenous 0.9% saline). This audit reinforces the need for strategies to improve the accuracy of fluid balance monitoring and adequate fluid administration.