The aim of this study was to explore and compare initial treatment effects of captopril (Tensiomin) and sodium dimercaptosulphonate (DMPS) on a relatively large series of Wilson's disease inpatients. Two important markers of anticopper efficacy: serum sulphydryl and 24 h urinary copper levels in the patients were evaluated before and after treatment. The patients were randomly subdivided into 4 groups to allow statistical analysis (ANOVA) of the values recorded. The protocol was an open-label study of all the patients treated for 8 weeks (i.e., all the patients except those in the no-drug group), and a further six-month follow-up (post hospitalization) of the 14 patients administered captopril. Several copper-related variables were studied to evaluate the effect of the drugs on copper, and several biochemical and clinical variables were studied to evaluate potential toxic effects. Captopril was found to have a significant anticopper effect and did not markedly raise serum sulphydryl levels within this limited patient sample; the anticopper efficacy of captopril was, however, found to be markedly lower than that of DMPS; DMPS was found to raise the patients' serum sulphydryl and urinary copper levels. Evaluation of data from individual patients revealed evidence of a toxic side effect in only 1 patient, treated with DMPS, who exhibited transiently raised serum alanine aminotransferases, while no serious adverse events, upstanding syncope, irritating cough and leukopenia induced by captopril were noted. The results obtained in this four-group sample suggest that captopril might be a mild anticopper agent for Wilson's disease, possibly relieving the hepatic portal hypertension, but that DMPS has a greater field of anticopper efficiency than captopril. The authors also discuss recent experience of the overall treatment in China.