Primary adenocarcinoma of the urinary bladder. A clinicopathologic analysis of 72 cases. Adenocarcinomas account for approximately 2% of primary epithelial malignancies of the urinary bladder. The clinicopathologic features of 72 cases treated at one institution are reported; 22 cases were evaluated immunohistochemically. Twenty-four tumors were urachal and 48 nonurachal. The cases were analyzed according to their stage at presentation, histologic type, and mucin staining; they were tested immunohistochemically to determine their reaction to carcinoembryonic antigen, Leu-M1, prostate-specific antigen, and prostatic acid phosphatase. Tumor stage was a highly significant predictor of outcome (P = 0.001). Nonurachal tumors tended to have a worse outcome than urachal, but the difference was not statistically significant (P = 0.07). Histologic type was not a significant predictor of outcome (P = 0.10). For adenocarcinoma of the urinary bladder, stage was the most significant predictive factor; separating urachal from nonurachal tumors was important, but mucin histochemistry and immunohistochemistry did not help in this distinction. On occasion, a few tumors may react with some polyclonal antibodies to prostate-specific antigen; thus these results must be interpreted with caution. In these instances, the possibility of using highly sensitive and specific monoclonal antibodies such as the one employed in this study should be considered. 