We report the terminal neurological impairment, amount of penicillamine taken, neuropathology and cerebral copper content of eleven patients with Wilson's disease treated for as long as 17 years. Therapy was accompanied by complete resolution of neurologic symptomatology in five patients and significant improvement in the neuro-psychiatric manifestations in six. Abnormal glial cells were seen in all the brains; gross or micro-cavitary changes were present in the putamina of eight. Of the four sets of observations, there was virtually no correlation between the degree of neurologic dysfunction - if any - in the months before death and either the amount of penicillamine taken or the cerebral copper content. There was, however, a fair degree of correlation between the severity of the neuropathologic findings and cerebral copper content.