Nomograms have been designed to provide rational and consistent guidelines for the use of phototherapy in the management of neonatal hyperbilirubinemia. In the management of 195 neonates in the first week of life, phototherapy, given according to these nomograms, was successful, except in some severe cases of Rhesus incompatability, in controlling hyperbilirubinemia in both premature and term neonates. When compared to the more random use before the introduction of the nomograms, phototherapy was reduced significantly without an increase in the requirement for exchange transfusions.