A case of ventro-peritoneal (V-P shunt) shunt insufficiency with dizziness and sensorial hearing loss is reported. The patient was a sixteen-year-old boy who had been diagnosed as hydrocephalic at six of age. Subdural space-peritoneal shunt was performed in February 1980, but because of the insufficiency, V-P shunt was subsequently required in September 1984. He began to experience dizziness in the middle of September 1995, which worsened with both standing and sitting. While his dizziness was improved in the supine position, however, it was gradually accompanied by progressive headache, nausea and vomiting. The patient subsequently admitted to a hospital, where a brain CT scan revealed narrow and slit-like ventricles. Further exacerbation of a month resulted in transfer of the patient to the department of a neurosurgery in Kanagawa Rehabilitation hospital and consulted for a neurlo-otological examination. Directional nystagmus detected during the initial examination had disappeared but left-sided positional horizontal nystagmus was found the following day. The eye tracking test revealed ataxia while the optokinetic pattern was lightly impaired. The result of the caloric test were normal. The right ear showed sensorial hearing loss at all frequencies which was more marked in the lower frequencies. The left showed sensorial hearing loss in the lower frequencies. The patient's cerebral spinal pressure was 1-2 mmH2O in supine position and 0 mmH2O at thirty degrees with the head up. The patient's hearing loss was gradually recovered. After reconstruction of the V-P shunt, however, the hearing loss in lower frequencies remained. Although endolymphatic hydrops due to shut insufficiency was initially thought to have caused this patient's dizziness and hearing loss, the result of the caloric test was normal. The neuro-otological findings revealed the possibility that the dizziness originated in the cerebellum although the real cause remains uncertain. Fluctuating hearing loss without dizziness and vertigo has reported previously in a case of V-P shunt insufficiency. The observation suggested V-P shunt insufficiency can be clinically divided into two types, one of which the chief symptom was marked hearing loss without dizziness and the other one of which is characterized by hearing loss without dizziness.