Fluid therapy in children requires an understanding of certain basic principles to avoid adverse events. Careful consideration needs to be given to both the appropriate rate and composition of the fluids to be administered with frequent re-assessment. Parenteral fluid management is used to meet maintenance requirements, correct any deficit and replace ongoing losses. Non-osmotic secretion of antidiuretic hormone (ADH) may occur, particularly in critically ill children and those in the perioperative period, resulting in an inability to compensate for an inappropriate administration of free water. Excess free water administration may result in cerebral oedema, which is poorly tolerated in children due to the proportionally larger size of the brain within the skull, compared to adults. Hyponatraemic encephalopathy continues to occur in hospitalized children and is associated with severe morbidity and mortality. Early recognition and aggressive management of this condition is required with hypertonic sodium chloride and further care within a paediatric highdependency/intensive care unit. In the perioperative period concerns over hypoglycaemia have resulted in routine use of dextrose-containing solutions. However for the majority of children the stress response coupled with dextrose supplementation is likely to result in hyperglycaemia. Current recommendations regarding perioperative dextrose management are reviewed.