We reviewed retrospectively 12 patients with Wilson's disease diagnosed during a 16-year period (1974-1989). The prevalence rate was 0.6 per 100,000 individuals. Clinical onset was hepatic (50%) or neurologic (50%), but at diagnosis (6.4 years later) 67% of patients showed several clinical manifestations: hepatic, neurologic, renal and haematologic. Among the essential diagnostic indices we find false negative results for Kayser-Fleischer ring (25%), serum ceruloplasmin (8%) and total serum copper (34%). Ten patients were treated with penicillamine. This drug was effective and well tolerated, although one patient (10%) developed membranous nephritis and required to change successively to BAL and trien. In a 61 months follow-up 5 patients (42%) died from severe liver failure. Patients with poor prognosis had a diagnostic delay and a liver failure degree significantly greater than patients with good prognosis. Our results suggest the following conclusions: a) in Spain the prevalence rate of Wilson's disease is near the lower reported rate; b) the early diagnosis of Wilson's disease is rare; c) diagnosis should be made only when several essential indices are positive; d) early hepatic transplantation showed carried out in patients with acute or chronic severe liver failure.