A cross-sectional study from 27 newborn nurseries over two 2-week periods compared transcutaneous bilirubin values to serum bilirubin values obtained within two hours of the transcutaneous value. Only 11% of all transcutaneous values had a concurrent serum bilirubin value available. The mean difference between transcutaneous and serum bilirubin was 0.84 +/- 1.78 mg/dL. In around 2% of measurements the transcutaneous bilirubin was lower than the serum bilirubin by 3 mg/dL or more. The difference between the two methods was greater in African-American infants, and also varied with the brand of transcutaneous bilirubinometer used.