Involvement of the nervous system in the idiopatic hypereosinophilic syndrome is a common finding, peripheral neuropathy being the most frequent neurologic manifestation, usually appearing at the onset or following the appearance of eosinophilia. We describe here the case of a 42 year-old male patient with persistent eosinophilia 1500/mm3) for a period greater than six months in the absence of a known cause for the eosinophilia with end-organ injury, in whom the neurologic involvement preceded by months the elevation of peripheral blood eosinophil count, and consisted of peripheral neuropathy and the unusual involvement of a cranial nerve. There was severe distal wasting and weakness of the four limbs with sensory abnormalites which developed over a period of four months, along with left-sided deafness which was due to eighth cranial nerve involvement. Eletrodiagnostic studies showed generalized nerve involvement of the axonal type. Nerve biopsy did not reveal eosinophilic infiltration or vasculitic changes, suggesting that neurotoxic eosinophil products may play a role in the neuropathy. There was marked improvement of the eosinophilia and slight improvement of the sensorimotor disturbance in the course of corticosteroid therapy.