Most patients with Wilson's disease are treated with the potentially toxic cupriuretic agent penicillamine. The toxicity of zinc taken by mouth is low, and long term administration induces a negative copper balance. Two patients with severe neurological symptoms were given zinc sulphate by mouth three times daily in doses of 200 mg, later increased to 300 mg. One patient, a 21 year old man, started to receive zinc sulphate after his condition had deteriorated during treatment with cupriuretic drugs. The other, a 27 year old woman, was treated from the start with zinc sulphate. The conditions of both patients improved appreciably, and they were still receiving treatment with zinc sulphate roughly two years later. Effective depletion of body copper stores was shown by an intravenous radiocopper loading test and liver biopsy. No side effects were found. Wilson's disease may effectively be treated with zinc sulphate alone.