Vibrations of 60 Hz and 100 Hz were applied on the mastoid of healthy subjects, patients with unilateral peripheral vestibular lesions, with central lesions of different localizations, and patients with benign paroxysmal positioning vertigo (BPPV). In patients with unilateral peripheral deficit a horizontal nystagmus with a small torsional component beating generally to the not affected side could be observed. This nystagmus did not show adaptation during 40 s. The occurrence was more frequent using 60-Hz stimulations. This vibration-induced nystagmus did never occur in healthy subjects, seldom in patients with central vertigo, and only exceptionally in patients with BPPV. It is concluded that the finding of a vibration-induced nystagmus reflects a side difference of peripheral vestibular excitability.