The aim of perioperative fluid administration is to maintain adequate intravascular volume to ensure acid-base and electrolyte equilibrium, and optimize oxygen delivery. Current practices are dictated by an algorithmic approach, taking account of pre-operative deficit, maintenance requirements, and extrapolated third space losses. Recent studies suggest that current strategies may result in excessive administration of both fluids and electrolytes, and that commonly observed postoperative weight gain is a manifestation of the injudicious use of parenteral fluids. The great fluid debate continues to rage.