Antigenic potential of a recombinant human erythropoietin (rhEPO) produced by Dong-A charm. Co. Ltd. was examined by active systemic anaphylaxis (ASA) test in guinea pigs, mouse-rat passive cutaneous anaphylaxis (PCA) reaction and passive hemagglutination (PHA) test. In ASA test, rhEPO induced the signs of restlessness, rubbing or licking nose, sneezing and coughing in the animals immunized with rhEPO 1000 lU/kg alone or rhEPO 1000 lU/kg incorporated into Freund\\`s complete adjuvant. In the mouse-rat PCA test, only one of six sera from the animals immunized with rhEPO 1000 lUng incorporated into Alum showed positive result. In the PHA test, rhEPO revealed negative results in all of the rhEPO-immunized groups. From these results, rhEPO was considered to produce IgE in guinea pigs and mice, but not IgG and/or IsM in mice. The results of this study were similar to those of the other recombinant human erythropoietin and these positive results were thought to be caused due to the fact that rhEPO were heterogeneous proteins to guinea pigs and mice. Considering the fact that rhErO has an identical structure with indigenous human erythropoietin, rhEPO is not thought to cause immunological problems in clinical use.