Our clinical observations disclosed that most newborn infants showed scaling on at least some parts of the body. To clarify the mechanism for such xerosis, we performed measurements of high-frequency conductance (Gx), which assesses the skin surface hydration and evaporative water loss from the skin. The skin of newborns showed surprisingly lower Gx values and evaporative water loss than those of adults or 1- to 6-month-old infants in a warm environment. These findings may be explained partly by low eccrine activity, which has been reported as characteristic of newborn skin. However, defective stratum corneum function, such as reduced water-holding capacity as demonstrated by the in vivo water sorption-desorption test, also seems to be responsible for the development of dry skin in newborns.