We examined the distribution of high- and low-molecular-weight cytokeratins, vimentin, and carcinoembryonic antigen (CEA) in normal endometrial glands and endocervical glands (20 cases each) and in endometrial and endocervical adenocarcinomas (29 cases and 15 cases respectively). Low- and high-molecular-weight cytokeratin staining was present in normal endometrial and endocervical epithelium and in carcinomas. Coexpression of vimentin and cytokeratin was universally present in normal proliferative endometrial glands, with marked decrease or absence of vimentin staining in secretory phase patterns. Vimentin staining had a perinuclear distribution within the cells, in contrast to the cytokeratins, which stained diffusely. Vimentin was found in only 65% of endometrial adenocarcinomas. Staining was typically focal as well as regional in portions of the tumors. Vimentin was never observed in normal or neoplastic endocervical epithelium. Ultrastructural studies corroborate the perinuclear vimentin immunostaining pattern we observed in endometrial adenocarcinomas. CEA staining results were similar to those previously reported. These data indicate that the presence of vimentin may readily distinguish endometrial from endocervical carcinoma and is diagnostically useful in the study of metastatic adenocarcinomas.