In three psychophysical experiments, cerebellar patients were impaired in making perceptual judgments of the velocity of moving stimuli. Performance was normal when the judgment concerned the position of the stimuli (Experiment 1). The dissociation between the velocity and position tasks suggests the cerebellar group was selectively impaired in velocity perception. EOG data were obtained in Experiments 2 and 3 to assess whether the deficit was oculomotor in origin. Perceptual errors were not correlated with the occurrence of intrusive eye movements. These results provide a novel demonstration of the role of the cerebellum in perceptual functions that require precise timing.