Copper-64 studies are presented of 2 patients with non-Wilsonian movement disorder and with abnormal copper handling. Both patients differed from the usual phenotype of non-Wilsonian low copper movement disorder as they had choreiform movement disorders with an onset in the first decade; one patient lacked significant intellectual impairment. Both patients had reduced serum total copper and marginal free copper and caeruloplasmin levels, and both patients were capable of incorporating 64Cu2+ into caeruloplasmin but the second case did so at markedly reduced level. Both showed slightly increased basal and stimulated urinary copper loss compared to normal controls with the rate in patient 1 being capable of leading to copper depletion. Liver copper content was normal in both cases. These 2 patients add to the reports of cases with copper deficiency and movement disorder in whom copper chelation therapy is unlikely to be beneficial.