The effect of body tilting on physiological functions was studied in 32 healthy, full-term neonates at 2 and 24 h of age. The neonates were placed in the supine position and the physiological functions were measured in the sequence of -30 degrees (head-down), 0 degree and 30 degrees (head-up) tilts. Arterial oxygen saturation and respiratory rate were comparable in the vaginal delivery and caesarean section groups. The baroreceptor responses were similar in the neonates delivered vaginally and by caesarean section. Mean heart rate increased on 30 degrees up tilting and the responses tended to be larger at 24 h compared with those at 2 h of age, but these differences were not significant. At 2 h of age, mean systolic and diastolic blood pressures decreased on 30 degrees up tilting. At 24 h of age, mean systolic and diastolic pressures decreased on up tilting (from -30 degrees to 0 degree) and the values were sustained on further up tilting (from -0 degree to 30 degrees). The present results indicate that baroreceptor reflexes are present from birth and the responses tend to be less developed at 2 h than those at 24 h of age.