['Numerous studies have demonstrated cerebellar activity during implicit motor learning, but few have addressed its specific role. The purpose of this study was to determine if specific components (spatial or temporal) of an implicit motor-tracking task were affected by cerebellar stroke.', 'The authors studied the performance of individuals with unilateral cerebellar stroke (n = 7)and a control group (n = 10) across 3 acquisition days and at a delayed retention test as they practiced a unimanual tracking task with the contralesional upper extremity.', 'After cerebellar stroke, participants demonstrated reduced tracking errors for repeating sequences compared to random sequences; however, decomposition of tracking performance into temporal and spatial components revealed persistent deficits in tracking time lag despite improved spatial accuracy. A lesion analysis showed that the dentate nucleus was the only common region affected by all cerebellar strokes.'] Does cerebellar stroke impair temporal but not spatial accuracy during implicit motor learning?