Thirteen of 22 patients with Wilson's disease had no history or clinical evidence of psychiatric disorder, while nine patients had various psychiatric diagnoses. Five of these improved psychiatrically with dietary and pharmacological treatment for hepatolenticular degeneration. Seventeen patients underwent psychometric testing; 13 were retested at various intervals after the initiation of treatment with a low-copper diet and penicillamine. Except for one patient who was mentally retarded, all patients showed slightly improved performance on intelligence tests after long-term treatment.Abstract Teaser