Transepidermal water loss (TEWL) is a simple noninvasive measurement of inside-out skin barrier function. The goal of this research was to establish normal values for TEWL in early life using data gathered from the Cork BASELINE Birth Cohort Study. TEWL was recorded in a standardized fashion using a well-validated open-chamber system. A mean of three readings was recorded from 1,036 neonates (37-42 weeks gestational age) and 18 late preterm infants (34-37 weeks gestational age) within 96 hours of birth in an environmentally controlled room. Full-term neonatal TEWL measurements have a normal distribution (mean 7.06 ± 3.41 g of water/m2 per hour) and mean preterm neonatal TEWL measurements were 7.76 ± 2.85 g of water/m2 per hour. This is the largest evaluation to date of TEWL in a normal-term neonatal population. It therefore constitutes a reference dataset for this measurement using an open-chamber system.