The reactivity of a panel of five mouse monoclonal antibodies (mAb) produced to human ovarian and endometrial cancer cell lines was analyzed on frozen sections of normal adult and fetal tissues and on tumor sections using immunofluorescence and immunoperoxidase procedures. mAb MH99 was reactive with almost all types of epithelial cells and stained all epithelial tumors examined. mAb MH94 reacted mainly with secretory epithelia and was unreactive with the epithelial cell layer of normal ovaries. In contrast, approximately 50% of epithelial ovarian tumors and the lining cells of inclusion cysts were positive. mAb MF61 was positive only on the endometrium and noncellular follicular secretions or colloid of the thyroid among normal tissues examined. A subset of ovarian tumors was positive with this antibody. mAb MF116 gave no reactivity with normal tissues within the sensitivity of the assay. MF116 was expressed on a proportion (44%) of ovarian carcinomas of various histological types. These antibodies provide an initial panel for the immunohistological analysis of ovarian cancer.