A boy 16 years old with Wilson's disease with serum ceruloplasmin 9 mg/100 ml, serum copper 50 mu g/100 ml and urine Cu 350 mu g/24 h was given a diet with 1.6 mg Cu daily and 200 mg zinc sulphate by mouth 3 times daily before meals. The 64Cu loading pattern suggested reduced absorption of Cu. After 3 months on Zn, neurological status was not changed, serum ceruloplasmin was 4.5 mg/100 ml, serum Cu 35 mu g/100 ml and urine Cu 100 mu g/24 h. D-Penicillamine, 250 mg 3 times daily, was then given for 3 months. Urine Cu increased to 1700 mu g/24 h and the intravenous 64Cu test suggested a decrease of the pool of accumulated Cu but the neurological condition did not improve. Zinc sulphate was reintroduced and clinical improvement was evident within 1 month. The pool of accumulated Cu fell further. After 3 months, clinical condition had improved further and ceruloplasmin was 2 mg/100 ml. There was no toxic side effect.