It is well known that intratracheal aspiration increases pscychological and physiological steress of low-birth-weight babies. The purpose of this study is to investigate the impact of introduction of Aspiration index, described by Yoko-o, to staff nurses on avoidance of unnecessary intratracheal aspiration in low-birth-weight newborn babies with respiratory distress syndrome(RDS)within 72 hours after birth. The change of the interval of intratracheal aspiration and respiratory status of the 8 patients with RDS were compared before(4 pts)and after(4 pts)introduction of Aspiration index (Yoko-o index)from the clinical records and questionnaire to the staff nurses. Results: before introduction of aspiration index, the interval of intratracheal aspiration for the newborns with RDS ranged from 2.3 to 3.4 hours. The half of the reason to attempt to intratracheal aspiration was not based on the medical condition of the patients but only from the working timeframe of the nurses. After introduction of aspiration index, however, that of intratracheal aspiration ranged from 4 to 8hours. No respiratory compromise or complications such as atelectasis was found even after extending the aspiration interval. Conclusion: The introduction of aspiration index to newborn cases with RDS could avoid unnecessary intratracheal aspiration without causing respiratory compromise. The further investigation is required to determine the more optimal aspiration procedures, taking account to the individual difference of the each newborns.