The report deals with 22 cases of two-phase head-shaking nystagmus. The results can be summarised as follows: 1. The two-phase head-shaking nystagmus is only found in connection with peripheral-vestibular disorders and particularly with unilateral disorders. It occurs only temporarily in the course of the vestibule disorder and may be observable for several months. 2. The head-shaking nystagmus, which follows immediately after the head-shaking (first phase), is to be considered a deficiency nystagmus. After a short period of latency after the disappearance of the first phase, a nystagmus in the opposite direction appears (second phase). This is considered to be a recovery nystagmus. 3. In the case of unilateral labyrinth lesions, the direction of nystagmus of the second phase of two-phase head-shaking nystagmus indicates the side of the lesion. The functions of the diseased labyrinth, however, have not been completely destroyed in this case. In the case of bilateral lesions, the direction of nystagmus of the second phase probably points toward the more heavily damaged side. While it is found only rarely, the two-phase head-shaking nystagmus thus permits reliable diagnosis and detection of the probable side where a peripheral vestibule disorder is located.