Disorders of fluid and electrolyte are common in neonates. Proper understanding of the physiological changes in body water and solute after birth is essential to ensure a smooth transition from the aquatic in utero environment. The newborn kidney has a limited capacity to excrete excess water and sodium and overload of fluid or sodium in the first week may result in conditions like necrotizing enterocolitis and patent ductus arteriosus. The beneficial effect of fluid restriction on the neonatal morbidity has been shown in multiple clinical trials. Simple measures like use of transparent plastic barriers, caps and socks are effective in reducing insensible water loss. Guidelines for the management of fluids according to birth weight, day of life and specific clinical conditions are provided in the protocols.