Sex did not appear to affect survival of newborn infants who had respiratory distress syndrome (RDS) in severe form. Male premature infants with birth weights over 1,500 gm were three times more likely to have severe RDS than female infants. Race did not appear to alter the fatality rate among infants with severe RDS. The effect of birth weight on survival in RDS depended on how the scope of RDS was defined. When infants with the mild form of the syndrome were excluded, no significant decrease in fatality rates was observed as the birth weight increased from 1,251 to 2,250 gm. When the infants with both severe and mild forms of the syndrome were included, there was a very significant decrease in fatality rates as birth weight increased. This inverse relationship was related to fact that the ratio of mild to severe cases increased with the birth weight. Fatality rates were significantly higher among infants with severe RDS if self-sustaining, spontaneous breathing was delayed more than one minute after birth.