This study was performed to determine whether the use of continuous transcutaneous oxygen tension (tcPO2) monitoring could reduce the incidence of retinopathy of prematurity in preterm infants receiving oxygen therapy. A total of 296 infants with birth weights less than or equal to 1,300 g were randomly assigned to a continuous monitoring or a standard care group. Infants in the continuous monitoring group had tcPO2 monitored continuously as long as they required supplemental oxygen, and infants in the standard care group had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. Of 148 infants in the continuous monitoring group, 101 survived; of the 148 patients in the standard care group, 113 survived. Mean birth weights and gestational ages were similar for both groups. Duration of mechanical ventilation and oxygen therapy was also similar. The overall incidence of retinopathy of prematurity was 51% in the continuous monitoring group and 59% in the standard care group. As birth weight for infants greater than or equal to 1,000 g increased, a higher risk of retinopathy of prematurity developing was noted in the standard care group. Cicatricial retinopathy of prematurity developed in four infants in the continuous monitoring group and five in the standard care group. These results suggest that continuous tcPO2 monitoring may reduce the incidence of retinopathy of prematurity in infants with birth weights greater than 1,000 g but not in the smaller infants in whom this complication occurs more frequently and is more severe.