With the aid of th positiogram, a quantitative recording of th positional test, it was possible to study the intensity of nystagmus in three acute vestibular diseases (vestibular neuronitis, Meniere's disease and sudden hearing loss with vestibular involvement). Patients with vestibular neuronitis in the acute stage showed a higher intensity of nystagmus during the positional test than patients passing through the irritation stage of Menière's disease. Especially patients suffering from vestibular neuronitis complained also subjectively about such an intense vertigo that they were seized by a feeling of annihilation at the onset of the disease. Quantification of the nystagmus during the positional test allows the progress, constancy or remission of the findings to be identified during the follow-up checks. Protracted constant pathological results obtained during the positional test, or when they become progressive, constitute in the light of our experience an indication for neuroradiological clarification in order to rule out an acoustic neurinoma as a cause (especially when a unilateral sensorineural hearing impairment exists).