This chapter discusses the main types of eye movement paralysis resulting from brainstem lesions, and the related pathophysiology. The abnormalities are easily detected at the bedside by studying three main types of eye movements: saccades; smooth pursuit; and the vestibular ocular reflex (VOR). The chapter reviews eye movement disturbances due to cerebellar and cerebral hemispheric lesions, resulting in relatively more subtle syndromes. The stroke-related lesions that most often involve horizontal gaze are located in the cerebral hemispheres and the pons. The hemispheral lesions are most often relatively large hemorrhages or infarcts that include the lateral aspect of the frontal lobe and/or the deep basal ganglia-capsular regions. Outside the brainstem, a number of suprareticular structures, located in the cerebellum and the cerebral hemispheres, control eye movements. Damage to these structures results in saccade and/or smooth pursuit disturbances usually much more subtle than those due to brainstem lesions.