A REVIEW of the American literature of the last forty years has revealed only 10 cases of primary pleural effusion in infants under 1 year of age. All 10 cases were reported as spontaneous chylothorax. The case reported here is the only known one of primary pleural effusion in a newborn infant in which the effusion was nonchylous. REPORT OF A CASE E. W. was born on Sept. 16, 1947, at the Bronx Hospital by normal spontaneous delivery. The child breathed and cried spontaneously. A physical examination fifteen hours after birth revealed no abnormalities other than severe substernal retraction on inspiration and some dulness over the right side of the chest compared with the left. A roentgenogram of the chest (fig. 1 A) was made on the second day of life. There was a shadow in the right side of the chest due to a moderate-sized pleural effusion surrounding the