Transcutaneous bilirubin index measurements (TcBI) were determined in ABO-incompatible term white newborn infants who had an indirect Coombs' test for detection of ABO incompatibility (ABO test) performed on cord blood. Serial transcutaneous measurements in the first 72 hours of life in 63 ABO test positive (group I) and 31 ABO test negative (group II) infants were compared with a control group of 109 term ABO compatible infants (group III). During the first phase of this study, the accuracy of TcBI was confirmed in 33 infants who had serum bilirubin determinations demonstrating a correlation coefficient of r = 0.93 between the jaundice meter index reading and total serum bilirubin. Determination of total serum bilirubin using TcBI did not show any statistically significant differences when groups I, II, and III were compared for maximum serum bilirubin values. These results reveal that a positive ABO test does not increase the predictive value of hyperbilirubinemia in ABO-incompatible white newborn infants.