We examined the eyes of all infants in our Neonatal Intensive Care Unit from 1979 to 1981 who were premature and/or had exposure to increased ambient oxygen. From these 1,012 neonates, 19 were found to have Grade III or worse acute retinopathy of prematurity (ROP) in at least one eye. We studied the graphic relationship of the mean daily values for blood Pc02, Pa02, PC02, and pH and the production of retinopathy of prematurity in these infants and compared the results with a similar group of infants who had similar birthweight, gestational age and Vitamin E administration. The comparison group patients were in the hospital during this same period of time and did not have Grade III ROP. There was no characteristic level, peak or pattern of these values that could identify or predict which infants would develop ROP.