This study determined the incidence of retinopathy of prematurity (ROP) in 2,958 admissions to the Newborn Intensive Care Unit of the James Whitcomb Riley Hospital for Children, Indianapolis, between January 1976 and December 1979. Among 2,484 survivors, acute ROP developed in 72 (2.9%); 60 (83%) of these newborns had birth weights of less than 1,500 g. The incidence of acute ROP among survivors with birth weights of less than 1,000 g (28%) was approximately three times that of the survivors with birth weights between 1,001 and 1,500 g (10.1%). The overall incidence of blindness was 4.5% of surviving infants less than 1,000 g and 1.2% of those surviving with birth weights of 1,000 to 1,500 g. Evidence of the strong influence of immaturity and low birth weight on the risk of development of ROP is reaffirmed. Increasing survival of the most susceptible infants may be the factor contributing most to the overall incidence of ROP.