PURPOSE: As there are some reports that music affects some physiological parameters and behavior of preterm infants, we have attempted to evaluate the effect of soothing classic music on the behavior and initial weight loss of full term infants. METHODS: A clinical study was conducted on newborn infants born at Youngnam University Hospital from July to August, 1999. Forty normal full term infants were randomly divided into two groups : music group and control group. During observation, infants in both groups were cared for in isolettes. Infants in the music group listened to Chopins Nocturnes after birth for 3 days. Observations were made for 60 minutes starting at 15 minutes after feeding, between 12 and 24 hours of age. Every minute during the observation, heart rate and arterial oxygen saturation were monitored by pulse oximeter, and behavioral states were evaluated using Brazelton's Neonatal Behavioral Assessment Scales. Induction time and duration of sleep were measured. Body weight was measured daily in the morning. RESULTS: Arterial oxygen saturation was higher in the music group than the control group(97.8+/-0.2% vs 96.8+/-0.3%). There was no significant difference in heart rate between them(120.2+/-6.5 vs 121.7+/-6.4). Sleep induction time was shorter(8.9+/-12.9 vs 21.4+/-14.4 minutes) and duration of sleep was longer in the music group(44.3+/-13.8 vs 27.6+/-11.9 minutes). Duration of crying was shorter in the music group(1.1+/-1.3 vs 2.6+/-2.5 minutes). Frequency of the changes in the behavioral states was lower in the music group(10.0+/-4.0 vs 16.5+/-6.1). Initial weight loss rate was smaller in the music group(0.095+/-0.033 vs 0.128+/-0.033% of body weight per hour). CONCLUSION: Soothing classic music induced sleep easily and maintained sleep longer and decreased behavioral changes. Decreased behavioral changes and longer sleeping time might cause less energy expenditure and reduce initial weight loss.