Quantitative measurement of eye movements is fundamental to understanding ocular motor control. Our method of electro-oculography permits vestibular, optokinetic, and saccadic responses to be recorded visually, graphically, and electronically with computerized analysis of the results. Studies in the past year have emphasized the contrasting abnormalities in patients with cerebellar lesions and those with progressive supranuclear palsy. The former involves primarily the visually monitored systems (e.g. pursuit) whereas the latter involves primarily the saccadic system (e.g., volition). An incidental study has also revealed contrasting abnormalities in patients with Gaucher's diease and with a form of Niemann-Picks's disease. The former are significantly accompanied by a disturbance in horizontal movements (at times simulating congenital ocular motor apraxia) whereas the latter are accompanied by disturbances similar to progressive supranuclear palsy. In neither case is the pathologic basis understood.