The purpose of this study was to inspect the effectiveness of the Developmental Care on the premature baby, under the following conditions; ①lowering the light stimulants to protect the infants on whole floor of the NICU. ②using the natural lighting rhythms. ③adjusting the care patterns, and ④positioning in good body balance and using the nesting positions. The study was made on the infants born before 35 weeks gestational age; 48 infants were the control, 55 infants were under the Study. Furthermore. the infants were divided into smaller groups of ①under the gestational age of 28weeks. ②the gestational age between 28 and 3lweeks. and ③the gestational age over 32 weeks. They were compared on 5 conditions; the days of hospitalization. the average weight gain by day, the days required to month feeding. the days required to be out of the incubator, and the days used oxygen. The results were the following. 1. The care was not effective on the infants born before 28 weeks gestational age on all 5 conditions. 2. The care seemed to be effective, but the result did not show the clear difference in the infants of the gestational age between 28 and 31 weeks. 3. The infants born after 32 weeks gestational age showed significantly the shorter days of the hospitalization and the shorter days in the incubator. 4. All infants showed the increasing average weight gain in good percentage. 5. The premature infants those who were born before 32 weeks of gestational age require more personal Developmental Care such as NIDCAP.