We studied the cause of death in a consecutive series of 164 patients with Wilson's disease (WD) diagnosed over an 11 year period. A total of 20 [12% (95% CI 10.3-16.0)] died during the observation period. The relative survival rate of all patients in our group was statistically smaller than in Polish population. The main cause of death was the diagnosis in advanced stage of disease, but in six patients presenting with mild signs, we observed the progression of the disease despite treatment. There was no difference in mortality rate in patients treated with d-penicillamine or zinc sulphate as initial therapy. The prognosis for survival in the majority of WD patients is favourable, provided that therapy is introduced early.