The ideal treatment for hyperbilirubinemia of prematurity would be a safe and simple method for preventing its occurrence. In 1958 it was first demonstrated that serum bilirubin concentrations of newborn infants can be reduced by exposure to light. This treatment has not been widely used because of doubts as to its effectiveness and concern for the possible toxicity of the photochemical decomposition products of bilirubin. Recent experimental evidence indicates that these products are non-toxic. A controlled clinical trial has been carried out among 111 premature infants to test the effectiveness of artificial blue light in preventing hyperbilirubinemia of prematurity. Treated infants were placed in light from 12 to 144 hours of age and serial bilirubin determinations were carried out. The control (58 infants) and treated (53 infants) groups were comparable with respect to birth weight, gestational age, fluid intake, and weight loss. The results indicate a statistically significant difference between the groups. By taking advantage of this alternate route of elimination of bilirubin in the newborn infant, it should be possible to greatly reduce the need for exchange transfusion for hyperbilirubinemia of prematurity.