The asparagine-linked sugar chains of human erythropoietin produced by recombinant Chinese hamster ovary cells and naturally occurring human urinary erythropoietin were liberated by hydrazinolysis and fractionated by paper electrophoresis, lectin affinity chromatography, and Bio-Gel P-4 column chromatography. Both erythropoietins had three asparagine-linked sugar chains in one molecule, all of which were acidic complex type. Structural analysis of them revealed that the sugar chains from both erythropoietins are quite similar except for sialyl linkage. All sugar chains of erythropoietin produced by recombinant Chinese hamster ovary cells contain only the NeuAc alpha 2----3Gal linkage, while those of human urinary erythropoietin contain the NeuAc alpha 2----6Gal linkage together with the NeuAc alpha 2----3Gal linkage. The major sugar chains were of fucosylated tetraantennary complex type with and without N-acetyllactosamine repeating units in their outer chain moieties in common, and small amounts of 2,4- and 2,6-branched triantennary and biantennary sugar chains were detected. This paper proved, for the first time, that recombinant technique can produce glycoprotein hormone whose carbohydrate structures are common to the major sugar chains of the native one.