Sera of 17 patients with Wilson's disease and of 48 relatives were investigated as to a possible correlation between ceruloplasmin phenotypes and Wilson's disease. The control group included 727 healthy subjects. The results of the quantitative determination of ceruloplasmin confirmed the overlapping in the groups of so-called heterozygotes and controls known from the literature. The ceruloplasmin phenotypes in starch gel electrophoresis we observed were of the most common phenotype Cp BB in the patients as well as in the controls. Therefore, patients with Wilson's disease also show the normal Cp-phenotypes.