To examine the neuropsychological deficits of patients with Wilson's disease (WD), 19 neurologically impaired patients with WD were administered the Wechsler Adult Intelligence Scale (revised), Wechsler Memory Scale, Dementia Rating Scale, Wisconsin Card Sorting Test, Boston Naming Test, Trail Making Test, and Animal Naming Test. Their test scores were compared with those of 12 neurologically asymptomatic patients with WD and 15 normal controls. The neurologically impaired patients scored lower than did the control group on the Performance IQ, Full-Scale IQ, Dementia Rating Scale, and Trail Making Test, and they scored lower on the Wechsler Memory Scale than did both the asymptomatic and control groups. The major areas of deficit for the neurologically impaired WD group were in motor and memory functioning. Computed tomographic and neurologic examinations of the neurologically impaired patients with WD generally reflected abnormalities of the basal ganglia.