TAG-72 is a tumor-associated antigen that is expressed by secretory endometrium and most endometrial adenocarcinomas. We used immunohistochemical techniques to quantitate expression of TAG-72, estrogen receptor, and progesterone receptor in 21 normal endometria and 44 endometrial adenocarcinomas. In normal cycling endometrial glands, TAG-72 expression was related inversely to expression of receptors for estrogen and progesterone. This suggests that TAG-72 expression in normal endometrium may be hormonally regulated. Ninety-one percent of endometrial adenocarcinomas expressed immunohistochemically detectable TAG-72. The magnitude of TAG-72 expression did not correlate with other known prognostic factors in endometrial cancer such as histologic grade, depth of myometrial invasion, surgical stage, or steroid receptor status. The production of TAG-72 by most endometrial adenocarcinomas may represent nonspecific expression by cells that have dedifferentiated.