A 33-yr-old man undergoing anorectal surgery developed cauda equina syndrome and bilateral profound hearing loss after single-injection spinal anesthesia with isobaric bupivacaine. There was no pain on needle placement. Neurologic assessment found impaired sensation to pinprick in the perineal region, lower extremity paralysis, and bowel and bladder incontinence. In addition, he developed a bilateral profound hearing loss involving the low frequencies, with the left side more affected than the right side. Although hearing impairment can occur with cerebrospinal fluid leakage, the etiology of cauda equina syndrome is uncertain. The simultaneous occurrence of these events has not been previously reported.