A 46-year-old healthy man suffered from sore throat, fever and right otalgia. On the next day, he developed hoarseness and difficulty in swallowing. On the 6th day, he suffered from vertigo, nausea and vomiting associated with unsteady gait. He was admitted to the otorhinolaryngology department in our hospital and pointed out to have vesicles at his right ear. On the 13th day, he was referred to our service. On admission, no vesicles were noted at the right ear or pharynx. Neurological examination revealed mild nuchal rigidity and marked hoarseness, associated with poor elevation of soft palate and loss of pharyngeal reflex on the right side. He also had horizontal-clockwise rotatory nystagmus in primary gaze and ataxic gait. There was no hearing loss nor facial palsy. No other abnormal neurological findings were noted. The cerebrospinal fluid showed pleocytosis associated with increased protein. The viral antibody titre for herpes zoster was significantly elevated on 18th day in serum as well as in cerebrospinal fluid. Vertigo, nausea, vomiting, ataxia and difficulty in swallowing were all disappeared by the 25th day, whereas hoarseness was improved but still noted 6 months later. Among cranial nerves, trigeminal and facial nerves are the most commonly affected in patients with herpes zoster, but there have been a few reported cases of the 9th and 10th cranial nerve involvement in the literature. In these previously reported cases, all were written before the era of serological diagnosis, and herpes zoster was diagnosed by the vesicles at the ear or pharynx.(ABSTRACT TRUNCATED AT 250 WORDS)