Post-operative fluid and electrolyte therapy is an integral component of anaesthetic management and it can play a critical role in surgical outcome. Replacement of water, ions, protein and or electrolytes is necessary to overcome pathophysiologie effects of operation and to treat any undelying or associated medical disorders complicated by body flouid d e arrangement depending on the patient and procedure. There can be differences in the complexity of fluid therapy nec'ded for appropriate restoration intraraseular volume 1osses. The eassy will cover the following subjects: Physiology of body fluids ; types of intravenous fluids ; requirement of fluids in post-operative period ; disease specific fluid therapy ; monitoring of fluid therapy ; hazards due to fluid therapy.