Two sisters with Niemann-Pick disease type C were examined: the brain in one sister, who had died, was examined, and eye movements in the other, surviving sister were recorded. Ocular motor recordings showed marked slowing of vertical saccades with relative sparing of horizontal saccades, pursuit, and the vestibulo-ocular reflex. Neuropathological findings included glial fibrillary lesions in the area of the posterior commissure and neuronal loss in the rostral interstitial nucleus of the MLF with preservation of the interstitial nucleus of Cajal and ocular motor complex. These neuropathologic findings correlate well with our current understanding of the anatomy and physiology of the supranuclear control of vertical gaze.