The clinicopathologic and immunohistochemical features of 16 pure adenocarcinomas primary in the urinary bladder were reviewed. Only 3 patients were found to have disease confined to the urinary bladder. Of 13 cases with follow-up only 3 are free of disease. Histologically, the tumors were classified as signet ring cell (3), colloid (3), colonic type (5), clear cell (1), and not otherwise specified (NOS, 4). Immunohistochemically, all tumors but one colloid carcinoma were immunoreactive for cytokeratin and epithelial membrane antigen, and most tumors were likewise immunoreactive for carcinoembryonic antigen. Eight cases were immunoreactive for Leu M1 antigen. Prostate specific antigen, S-100 protein, and placental alkaline phosphatase were uniformly negative. No correlation between immunohistochemical profile and histologic type or clinical outcome was found. The utility of immunohistochemistry and other pathologic findings is reviewed.