The circling-waltzing behaviour of the Shaker-2 mouse is suggested, at least in part, to be of peripheral origin. In this hereditary inner ear disease, degeneration of hair cells type I has been observed showing specific pathologic features: rod-shaped inclusion bodies and sensory hair fusion. Later, the hair cells type I are expelled into the endolymphatic space. A large number of sensory cells type II are morphologically normal. The failure of earlier investigators to demonstrate pathological changes in the sensory epithelia of this animal is likely to be due to the use of light microscopical methods only.