The role of peripheral information in smooth motor performance was analyzed in normal subjects and patients with deep sensory disturbance by the modified visually guided tracking method. The subject's task was to make the control cursor match the slowly moving target by elbow flexion movement. Performance of normal subjects was scarcely affected, but that of the patients was deteriorated by the withdrawal of the visual cue for handle movement. It is suggested that afferent information from the moving limb plays an important role in smooth and accurate tracking movements.