Mesonephric adenocarcinoma is a rare variant of cervical carcinoma with relatively few, well-documented cases reported. We describe the clinicopathologic and immunohistochemical features of 11 examples of this neoplasm, which occurred in women between the ages of 35 and 72 years (mean, 52 years). Most (64%) patients had abnormal vaginal bleeding. Eight tumors were stage IB, and one each was stage IIB and IVB; in one, the stage was unknown. Microscopically, the carcinomas showed various morphologies, most commonly a small tubular pattern or a ductal pattern resembling endometrioid adenocarcinoma; one tumor had an associated malignant spindle cell component. Ten neoplasms were adjacent to hyperplastic mesonephric remnants. Follow-up in 10 cases showed six patients to be alive without evidence of recurrence after a mean of 4.8 years. The patients with stage IIB and IVB disease had local recurrences after 2.2 and 0.7 years and died of progressive disease at 3.2 and 0.8 years, respectively. In a patient with stage IB disease, a mediastinal metastasis and a malignant pleural effusion developed 5.6 years after diagnosis, and the patient died of disease at 6.2 years. Another patient with stage IB disease and a positive vaginal cuff margin that recurred locally after 1.7 years received chemotherapy and was alive and clinically free of disease at 2.5 years. Mesonephric adenocarcinomas were immunoreactive for epithelial markers (AE1/3; CK1, CAM 5.2, cytokeratin 7, and epithelial membrane antigen) (100%), calretinin (88%), vimentin (70%), androgen receptor (33%), and inhibin (30%, focal staining). No immunostaining was detected with cytokeratin 20, estrogen receptor, progesterone receptor, and monoclonal carcinoembryonic antigen. This staining profile is similar to that of mesonephric remnants and may be useful in the distinction of mesonephric carcinoma from mullerian endometrioid adenocarcinoma, with which it may be confused.