To determine a phenotypic difference between normal endometrium and endometrial adenocarcinoma, a new monoclonal antibody (MSN-1) was produced by immunizing a new endometrial cancer cell line (SNG-II), which was established in 1981 from a 43-year-old Japanese woman with stage II uterine endometrial cancer. MSN-1 recognized the Lewis-b carbohydrate moiety on the cell surface glycolipid and seldom reacted immunohistochemically with normal endometrium but with about 90% of endometrial cancer cases. By application of MSN-1 to flow cytometry, the possibility of differentiating endometrial normal cells from cancer cells was demonstrated.