Twenty-two patients with bladder carcinoma were examined by MR imaging and CT to determine the degree of parietal involvement. The results were then compared with the surgical and histological findings. A classification in CT and MR stages was elaborated in order to supply corresponding models to clinical TNM staging. Three groups were thus formed, corresponding to the evolutive phases of the tumor. The first MR group included T1-T2 forms (accuracy: 75%); the second group included T3a forms (accuracy: 75%), and the third T3b-T4 forms (accuracy: 90%). Overall MR accuracy was 81.81%. The first CT group included T1 forms (acc. 71.42%), the second group T2-T3a forms (acc. 60%), and the third group included T3b-T4 forms (acc. 90%). Overall CT accuracy was 77.27%. MR imaging proved thus more accurate than CT in the staging of bladder tumors, especially thanks to its allowing deep muscular involvement to be assessed.