The clinical and electronystagmographic findings of 255 patients with paroxysmal positional vertigo are presented. We believe the disorder should be diagnosed on the basis of the history and clinical findings since we did not find any characteristic electronystagmographic findings other than the recording of an actual attack. Our observations lead us to believe that there is only one type of attack. We conclude that the nystagmus which occurs during the attack is generated by stimulation of the posterior semicircular canal of the lowermost ear.