BACKGROUND: Unsteadiness during standing and walking is a frequent complaint of patients with polyneuropathy (PNP). OBJECTIVE: To determine whether balance disorders in patients with PNP may be caused by reduced proprioceptive input from the feet alone or whether impaired vestibular input, resulting from involvement of the vestibular nerve, can be an additional factor. METHODS: A total of 37 patients (mean age 65 years +/- 12 SD; 12 women) with electrodiagnostically confirmed PNP (predominantly axonal: 18; predominantly demyelinating: 19) underwent horizontal search-coil head-impulse testing, which assesses the high-acceleration vestibulo-ocular reflex (VOR). RESULTS: Relative to a healthy comparison group, the gains (eye velocity divided by head velocity) of the horizontal VOR were reduced in 27 of 37 patients (unilateral: 13; bilateral: 14). The percentages of patients with unilateral or bilateral VOR deficits were not significantly different between patients with axonal or demyelinating PNP. CONCLUSIONS: Two thirds of patients with axonal or demyelinating polyneuropathy (PNP) showed unilateral (approximately 50%) or bilateral (approximately 50%) gain reductions of the horizontal high-acceleration vestibulo-ocular reflex. This finding suggests that, in many patients with PNP, the neuropathic process includes the vestibular nerve. Such information is highly relevant for subsequent physical therapy, since vestibular exercise improves balance control and reduces disability.