Since the introduction of the intensive perinatal care, the surviral rate of the infants weighing less than 1500 gm at birth has improved substantially. However, pulmonary diseases remain to be the major causes of the high mortality of these low birthweight infants. In order to systematically assess an epidmiologic distribution of the pulmonary diseases in these very low weight prematures, we have analyzed the chest x-rays of 102 infants weighing less than 1500gm. These consisted of 30 with extreme low birth weight (ELBW) weighing less than 1000gm and 72 with very low birth weight (VLBW) weighing 1001-1500gm. The survival rate of ELBW and VLBW was 10% and 49%, respectively. Seventy of 102 infants had abnormal findings in the chest x-ray. Forty-eight had idiopathic respiratory distress syndrome (IRDS), 8 immature lung, 6 Wilson-Mikity syndrome, 4 pneumonia, 2 pulmonary hemorrhage, 1 congenital heart disease, and 1 suspicious Pierre-Robin syndrome. seven out of 48 infants with I DS had persistent ductus arteriosus and in only 2(30%) of 7 cases were alive. Endotracheal intubation and assisted ventilation application for the treatment of IRDS resulted in pulmonary interstitial emphysema in 4 infants and pneumothorax and/or pneumomediastinum in 4 infants. Displacement of endotracheal intubation showed lobar and/or unilateral lung atelectasis in 8 infants and a case of accidental dislodgement of intubation tube into the esophagus resulted in air esophagogram and worsened lung aeration. In spite of the development of many sophisticated methods of diagnostic radiology, the chest x-ray was still the most valuable yet simple way of evaluating the pulmonary problems in these extreme and very low birth weight prematures.