Adenocarcinomas of the uterine cervix show a wide range of morphological features, and can be confused with endometrial adenocarcinoma in biopsy or curetting specimens. The objective of this study was to use tissue microarray technology to evaluate the immunoprofile of a large set of uterine adenocarcinomas with an extended panel of antibodies, comparing the profile of primary cervical and endometrial adenocarcinomas. A tissue microarray was constructed using paraffin-embedded, formalin-fixed tissues from 141 hysterectomy specimens. Duplicate 0.6-mm cores were obtained from 57 cervical adenocarcinomas (16 in situ and 41 invasive) and 84 endometrial adenocarcinomas. Tissue array sections were immunostained with 21 commercially available antibodies [B72.3, CD 99, carcinoembryonic antigen (CEA), c-kit, pancytokeratin, CK 5/6, CK 7, CK8/18, CK19, CK 20, CK 22, EMA, estrogen receptor (ER), KP-1, melan-A, p53, PLAP, S-100, synaptophysin, TTF-1, and vimentin] utilizing the avidin-biotin (ABC) technique. Hierarchical clustering analysis of the tumors was done based on the immunostaining results. Only ER ( P<0.001), CEA ( P=0.04), vimentin ( P<0.001), and CK 8/18 ( P=0.002) showed a significantly different frequency of positivity in endometrial relative to cervical adenocarcinomas. ER, vimentin, and CK 8/18 were more likely to be expressed in endometrial adenocarcinomas, while cervical adenocarcinomas more frequently expressed CEA. We were able to identify immunoprofiles that were highly specific for endocervical adenocarcinoma (ER(-), vimentin(-), CK 8/18(-), CEA(+)) or endometrial adenocarcinoma (ER(+), vimentin(+), CK 8/18(+), CEA(-)), but most tumors showed an intermediate, non-specific immunophenotype. Hierarchical clustering analysis was useful in the interpretation of these intermediate immunophenotypes. Papillary serous adenocarcinoma of the endometrium was less likely to express vimentin ( P=0.002) than endometrioid carcinoma of the endometrium.