One hundred and fifty deaf children between 5 and 16 years old of the 'Rudolf Mees' Institute were investigated in search of the Tullio phenomenon with nystagmus as a criterion. Seventy-six out of those 300 ears were positive. A functioning (calorically excitable) pars superior of the labyrinth was a 'conditio sine qua non' for this reflex. We may assume that deaf ears which show a positive Tullio phenomenon have a labyrinthine pathology of the Mondini-Alexander type and that this symptom is a pathologic one.