A 6 1/2-month-old boy with acquired immunodeficiency syndrome was treated with zidovudine for 12 months. He experienced a marked improvement in clinical and neurologic status. Auditory brainstem responses were recorded before, at 6 months, and after 12 months of therapy; interpeak latency I-V, which was initially delayed, demonstrated progressive shortening that was greater than could be attributed to maturation alone. Auditory brainstem response improvement after zidovudine therapy has not been reported previously.