When exposed to a cool environment, the newborn infant responds by nonshivering thermogenesis. The increased heat production is at the expense of body fuel and energy stores. A significant quantity of heat is lost from the head because of its large surface area and the high metabolic activity of the neonatal brain. The purpose of this study was to determine whether dry cranial heat loss could be significantly reduced by covering the head with highly insulated material, and to determine whether plastic lined hats decreased evaporative heat loss. A total of 46 fullterm and premature infants were studied. Hats insulated with material made of olefin and polyester reduced cranial dry heat loss by 73% and 63%. Plastic lined hats reduced evaporative heat loss by 68%. The insulated and lined hats proved to be a simple and safe method of effectively reducing dry and evaporative heat loss.