The role of computed tomography in the preoperative staging of bladder and prostate tumors is discussed and illustrated. The accuracy of judging perivesical tumor extent, various techniques of CT examination, and the clinical significance of evaluating local bladder extension are discussed. The CT evaluation of local periprostatic extension of tumor is examined in relationship to the type of planned therapy. A dynamic technique for lymphadenopathy evaluation is detailed. The accuracy of demonstrating lymphadenopathy by CT and its therapeutic impact on the surgical treatment of bladder and prostate malignancies are discussed.