BACKGROUND Neonates with ABO hemolytic disease are at greater risk for developing significant hyperbilirubinemia. We aimed to determine whether sixth hour transcutaneous bilirubin (TcB) could predict such a risk. METHODS TcB measurements were obtained at the 6th hour of life in blood group A or B neonates born to blood group O, rhesus factor compatible mothers. Subsequent hyperbilirubinemia was monitored and considered significant if a neonate required phototherapy/exchange transfusion. The predictive role of sixth hour TcB was estimated. RESULTS Of 144 ABO incompatible neonates, 41(OA, 24; O-B, 17) had significant hyperbilirubinemia. Mean sixth hour TcB was significantly higher among neonates who developed significant hyperbilirubinemia than those who did not (5.83±1.35 mg/dL vs. 3.65±0.96 mg/dL, P<0.001). Sixth hour TcB value >4 mg/dL had the highest sensitivity of 93.5% and >6 mg/dL had the highest specificity of 99%. Area under receiver operating characteristic curve was 0.898. CONCLUSION Sixth hour TcB predicts subsequent significant hyperbilirubinemia in ABO incompatible neonates.