Mediastinal tumor is a rare cause of severe respiratory distress in the newborn. A recent patient was transferred++ to our intensive care nursery with severe distress due to a large mediastinal teratoma. The presence of calcifications on the plain chest roentgenogram suggest the diagnosis. At two hours of age the tumor developed in the left hemi-thorax was completely removed. Microscopically it was a typical well differentiated+ benign teratoma, but the postoperative course was marked by a continuing respiratory distress due to a paralysed left diaphragm. This situation was surgically corrected by infolding the diaphragm at twenty days of life. At the fourth postoperative day the endotracheal tube was removed and the baby is now well with a normal chest. X-ray at six month of age. Because the rarity of this tumor in the newborn, because the possibility of antenatal echographic diagnosis, we record this experience and review the literature.