The relation between the yellow colour of the skin as measured by the Minolta Air Shields jaundice meter and the serum bilirubin concentration was investigated in 207 mature icteric, but otherwise healthy, newborns and the relationship between the changes in the meter readings and the changes in serum bilirubin concentration was studied in 99 of the infants. Good correlation was found both between the meter readings and the serum bilirubin concentration (p = 0.81), and between the changes in meter readings and the changes in serum bilirubin concentration (p = 0.69). The jaundice meter proved to be effective in predicting hyperbilirubinemia defined as serum bilirubin values 175 or 225 mumol/l, and was also effective in predicting increasing or decreasing serum bilirubin concentrations by sequential meter readings. The gestational age correlated slightly but significantly with the meter readings (p = -0.15) and with the serum bilirubin concentration (p = -0.15). However, these findings did not affect the action levels for use of the jaundice meter as a screening device for hyperbilirubinemia. The postnatal age and the birthweight did not significantly influence the meter readings.