Human amniotic epithelial (HAE) cells have great potential for successful use in cell therapy, since they do not cause acute rejection upon allotransplantation. However, to date, HAE cells have not well been studied. We previously reported that HAE cells produce erythropoietin (EPO), which is known to be a regulator of hematopoiesis, and that the induction mechanism of HAE cells is unknown, although EPO production from HAE cells is not increased by hypoxia which induces several cell types to produce EPO. In this study, we determined whether female sex hormones, including progesterone and 17beta-estradiol, affect the EPO production of HAE cells. Bioactive measurement of EPO activity in the culture supernatants of HAE-SV40 cells, which were immortalized by transfection with a simian virus 40 large T antigen, revealed that EPO bioactivity was significantly increased by treatment with progesterone, but not 17beta-estradiol. Treatment of HAE-SV40 cells with progesterone transiently increased the EPO mRNA level by fivefold, while there was no change in response to 17beta-estradiol. Furthermore, the progesterone receptor (PR)-B was detected in both HAE cells and HAE-SV40 cells by Western blotting. These results suggest that EPO synthesis in HAE-SV40 cells is stimulated by progesterone, but not by 17beta-estradiol, and thus it is highly likely that the EPO synthesis of HAE cells is also regulated by progesterone.