Ten newborn infants were given gentamicin intramuscularly. Over a postinjection interval of 12 hours, no significant change occurred in the total binding capacity of serum albumin for bilirubin or in concentrations of serum bilirubin levels. There was no correlation between concentrations of serum gentamicin and the total binding capacity or serum bilirubin. This study provides in vivo data that supports recent in vitro experiments showing that gentamicin does not alter bilirubin-albumin binding.