The purpose of this study was to evaluate the effects of sponge bathing on physiological (vagal tone, heart rate, heart period, oxygen saturation) and behavioural responses in newly born premature infants in the intensive care unit of a university hospital in South Korea. A convenience sample was taken of 40 infants who were between 27 and 36 weeks gestational age at birth and free of congenital defects. The infants' physiological parameters were recorded 10 min before, during and after bathing. To determine behavioural status, tools were modified from the instruments used in a previous study by Scafidi et al. (1990). Analysis of the results showed that the premature infants reacted to sponge bathing with decreases in vagal tone and heart period and increases in heart rate. Oxygen saturation did not demonstrate any remarkable alteration during bathing. Also, there were no significant differences in behavioural signs, motor activity and behavioural distress. Results of this study indicated that nurses in a neonatal intensive care unit should decide according to a premature infant's physiological state whether or not to give a sponge bath.