An understanding of the basic principles underlying fluid and electrolyte replacement in children is important for the operating room nurse who frequently prepares the intravenous for administration. The nurse may question why some physicians prefer to replace loss with dextrose in water while others feel some form of physiological salt solution is necessary.The purpose of this article is to provide the nurse with information upon which the selection of quantity and content of fluids and electrolytes in the operating room has been based. It also describes why pediatric pa-E J Bennett, MD, is associate professor a t the University of Illinois, Chicago, and director of pediatric anesthesia, University of Illinois Hospitals. H e received his medical degree from the University of Sydney, Australia. F Y Dalal, MB, i s assistant professor of anesthesiology, Stritch School of Medicine, Loyola University. Maywood, 111. H e was educated a t the University of Bombay, India.