Two siblings with Cockayne's syndrome (CS) are described. Both showed cachectic dwarfism, photosensitivity and progressive neurological dysfunction. The damped-rotation test revealed no vestibular nystagmus in one of them, and reduced per-rotatory nystagmus in the other. Neuropathological examination in the former subject disclosed neuronal loss with fibrillary gliosis in the vestibular nuclei, whereas neuronal degeneration was not apparent in the abducens nuclei, the oculomotor nuclei and the paramedian pontine reticular formation. Our findings suggest that CS might cause vestibular dysfunction as well as hearing loss and that the lesions in the vestibular nuclei might be related to the vestibular dysfunction.