Ten premature infants with low serum thyroxine levels (less than 84 nmol/L) were compared with 10 biochemically euthyroid infants to determine whether hypothyroxinemia in such infants can lead to alterations in the auditory pathway. The auditory pathway was studied between 6 and 11 wk of life by analyzing brainstem evoked potentials elicited by a 10/s, 75 dB above normal adult hearing level click stimulus presented at the infant's ears. Peak latencies of components I, III, and V and interpeak latencies I-III, III-V, and IV did not yield statistically significant differences between groups. The present study indicates that untreated neonatal hypothyroxinemia does not lead to abnormalities of auditory brainstem evoked response.