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Although it is well established that subjects with Parkinson's disease perform poorly on complex sensory-motor tasks, the extent to which this is due to visuoperceptual deficits is unclear. The authors measured the performance of 16 patients with Parkinson's disease, both on and off drugs, and 16 age and sex matched control subjects on preview and nonpreview tracking tasks and a nonmotor test of dynamic visuoperception. Order effects were controlled for by a randomized cross-over design. Performance on the perceptual task was measured in terms of perceptual resolution and was found impaired in the Parkinsonian group. The contribution of visuoperceptual function to tracking performance was removed using the concept of a visuoperceptual buffer-zone. The mean tracking error remained impaired on all tracking tasks and demonstrated that limitations in visuoperceptual function play only a minor role in the tracking errors in both Parkinsonian and control subjects. It is clear that the technique for determining the visuoperceptual component of performance on complex sensory-motor tasks has considerable scope for application in studies of a variety of brain disorders.