Primary signet ring cell adenocarcinoma of the bladder is a very uncommon tumor type. Only 20 cases have been reported to date. Two additional cases are described. One patient was diagnosed as having plastic linitis of the bladder. The interval between the onset of symptoms and diagnosis ranged from 2-8 months. Tumor stage was P4 N4 MO and P4 N4 M1 at the time of diagnosis and survival was 3 and 1 month, respectively. This is a tumor with a remarkable intramural proliferation, in the advanced stages at the time of diagnosis, and a poor prognosis. To date, no widely-accepted therapeutic approach has been established.