One of the biggest risks to the clinical application of embryonic stem cell research is the risk of tumor formation. Such tumors, known as teratomas, form because there exists embryonic stem cells that have not completely become the desired transplantable tissue. These undifferentiated cells have rightfully become a cause of great concern and threaten to stop the clinical implementation of embryonic stem cells. We have developed an antibody against such cells that is able to recognize and thereby remove these cells before transplantation. We found that using this antibody alone drastically reduces the frequency of teratoma-forming cells. However, when this antibody is coupled with two other antibodies, which also target embryonic stem cells, we are able to achieve complete removal of all teratoma forming cells. This work holds great promise to facilitate the clinical utilization of embryonic stem cell based therapeutics.