Adenocarcinoma of the urinary bladder is an uncommon, often aggressive urologic cancer. In an attempt to classify and define management of this tumor, 28 patients with vesical adenocarcinoma were studied. Excluded were patients with mixed transitional cell carcinoma and adenocarcinoma. Three major classes of tumor were identified: primary vesical adenocarcinoma, urachal adenocarcinoma, and extravesical adenocarcinoma involving the bladder. Signet ring cell tumors appeared to behave more aggressively than other cell types. Radical surgery was the most effective treatment.