Optokinetic nystagmus was evoked by a striped drum. The width of the stripes was varied between 4 and 30°. The amplitude of the nystagmus beats was strongly correlated with the logarithm of slow phase speed but not at all with the width of the stripes. Maximum speed of the fast phase was proportional to its amplitude. The maximum deviation of the eye from he midposition was never larger than about 15°. In the absence of visual information (caused either by total darkness, photocoagulation of the retina, or bilateral ablation of visual cortex and superior colliculus), the eye is continuously drifting but is always kept in the normal excursion range by fast movements, directed to the midposition. I concluded that fast eye movements in the rabbit act as a reset mechanism, independent of any visual control, and that an important function of the visual smooth pursuit system is to stabilize the eye position against drift.