Co-culture of human embryonic stem (ES) cells on mouse fibroblast feeders is the commonly used method for in vitro expansion of human ES cells in an undifferentiated state. However, it has potential risks of pathogen transmission from animals; thus, human cell-derived feeders have been employed to minimize this problem. In this study, we compared human placenta-derived feeders with bone marrow to demonstrate its effectiveness as feeders for in vitro long-term culture of human ES cells. We cultured a human ES cell line, SNUhES3, on human placenta-derived mesenchymal stem cell feeders and compared their culture efficiency with human bone marrow-derived feeders and control group (mouse fibroblast feeders, STO). The mean number of human ES cell colonies was 166 +/- 35 in the placenta feeders; this was significantly higher than bone marrow-derived feeders (87 +/- 16, p < 0.05). We could propagate the culture of SNUhES3 on the placenta feeders past the 50th week similar to control group. During the culture, the maintenance of undifferentiated state of SNUhES3 was demonstrated by the expression of SSEA-4, TRA-1-81, TRA-1-60, and Oct-4. However, we failed to propagate the culture of human ES cells on the human bone marrow-derived feeders past the 5th week. The efficiency of embryoid body formation was similar between placenta and control group, indicating the preservation of differentiation ability. Thus, placenta-derived feeders are more efficient for the long-term in vitro culture of human ES cells than bone marrow-derived feeders suggesting the possible role of placenta as a source for human cell-derived feeders.