This is a randomized, prospective, controlled study to compare the efficacy of single versus double halogen phototherapy in high risk patients admitted to a newborn intensive care unit. Eighty patients were allocated to receive single (N=43) or double (N=37) phototherapy. The groups were similar in clinical and laboratory characteristics. Total serum bilirubin (SB), hematocrit and total serum protein were assessed by microanalysis prior to the beginning of the study and at 6, 12, 18 and 24 hours of treatment. The percent decline of SB was significantly higher in the double phototherapy group. This difference is first noted at 12h of treatment (10% vs 1.8%, p< 0.01) and is acentuated at the end of the study (19.4% vs 1.6%, p< 0.0001). Weight loss, variations in the hematocrit and total serum protein were similar in both groups. Cutaneous rash and temperature instability were not noted among the patients studied. Our results demonstrate that double phototherapy is more efficient than single phototherapy in treating hyperbilirubinemia in high risk newborn infants.