Less is known about the mucin-type sugar chains attached to human erythropoietin as compared with N-linked sugar chains which structures and function have been well studied. In this study, we purified urinary human erythropoietin from three independent groups of aplastic anemia patients, and analyzed the structures of mucin-type sugar chains as well as that obtained from recombinant human erythropoietin produced by Chinese hamster ovary cells. Unlike the N-linked sugar chains, the mucin-type sugar chains are totally different between the urinary and the recombinant erythropoietins. All of the three independent samples of urinary erythropoietin contained oligosaccharides with the structures of +/- Neu5Ac alpha 2-->6GalNAc, while recombinant human erythropoietin contained those with the structures of Neu5Ac alpha 2-->3Gal beta 1-->3(Neu5Ac alpha 2-->6)GalNAc, Neu5Ac alpha 2-->3Gal beta 1-->3GalNAc, and Gal beta 1-->3(Neu5Ac alpha 2-->6)GalNAc.