Our data cannot be interpreted to support the use of free bilirubin determinations in a clinical setting. It is difficult to determine how Wennberg and Ahlfors used acidosis and free bilirubin to make a 60% correct prediction of kernicterus when we supplied very little acid-base information. Perhaps they interpreted our data to suggest that acidosis only occurred in the infants listed in table 4 of the paper. In fact, the 30 autopsied infants on whom our observations are based had very similar degrees of acidosis (Table).