Of 375 newborn infants in Korea General Hospital in the period of 6 months from March 1 to August 30, 1976. 304 newborn infants were available for the study of serum bilirubin level at the third day of the birth. The followings are results analyzed: 1) The mean value of serum bilirubin level estimated is 10.6mg%. The incidence of neonatal jaundice is estimated as 95.4 percent. 2) The premature infants reveal a marked elevation of serum bilirubin level. Conditions with increased level of serum bilirubin in variable degree include vacuum suction and/or forcep delivery, high or low hematocrit value, low Apgar scores, artificial resuscitation, cephalhematoma and spontaneous premature rupture of the membrance. 3) No relationship in serum bilirubin levels between differences in sex, body weight, number of pregnacies and ABO blood groups of mother and infant is present in this study.