Since auditory function can be assessed objectively by recording Auditory Evoked Potentials from the brainstem, we propose to study in term and premature neonates affected by hyperbilirubinemia. Such factors as development, hypoxia and therapy will be examined for their influences. Serum Bilirubin levels will be correlated with auditory function in an attempt to ascertain a more precise understanding of the mechanism of deafness in these infants. It is expected that a more precise index of Bilirubin toxicity will be found for purpose of treatment and prognosis. From those infants who succumb in the course of study, neuropathologic confirmation of the location and extent of CNS damage will be obtained.