Stage-specific embryonic antigens (SSEAs) are cell-surface molecules that exhibit lineage-restricted patterns of expression during development. SSEA1 provides a surface marker for mouse and human primordial germ cells and mouse embryonic stem cells. SSEA3 and SSEA4 act as surface markers for human embryonic stem cells (ES). The epitope recognized by the SSEA4 antibody is also expressed on the surface of human embryonal carcinoma (EC) cells, human embryonic germ cells (EG), mesenchymal stem cells (MSC), and in early neuroepithelium. In addition to recognizing human and mouse cells, germline stem cell-like cells from both juvenile and adult chicken testes were successfully stained with this antibody. Using series of purified glycolipids, a more refined epitope corresponding to a unique globo-series ganglioside was characterized. Besides being expressed in embryonic cells, this epitope is also present in human erythrocytes. This anti-SSEA4 antibody, clone MC813-70, was developed using mouse 4-8 cell embryos as immunogen and reacts with human and mouse SSEA4 antigen. This antibody provides an extremely useful tool for looking into differential expression of SSEAs in various embryonic cell populations.