An orthotopically transplanted, locally metastasizing rat bladder tumor model was developed to evaluate the extent of uptake of fluoro-deoxy-glucose (FDG) in bladder cancer. Significant uptake of FDG in localized bladder tumors in rats was shown, with an average tumor-to-blood ratio of 39 at 2 hours after intravenous FDG administration. Metastases (3 nodal and 1 peritoneal) also showed significant uptake of FDG, with an average metastasis-to-blood ratio of 21.7, and tumor involved-to-normal lymph node ratio of 5.3. Because FDG is excreted in the urine, urinary FDG potentially could prevent the use of FDG/positron emission tomography (FDG/PET) scanning for localized bladder cancer. Bladder lavage successfully reduced the retention of FDG in the normal rat bladder, with an estimated uptake ratio of tumor-to-normal bladder of 13.1 after 5 ml. saline irrigation. Based on these data, we performed an FDG/PET scan of a patient with biopsy proved recurrent intravesical bladder cancer after radiation therapy. Computerized tomography (CT) of the pelvis showed abnormalities consistent with radiation scarring and extravesical tumor. Due to the scarring, the extent of tumor growth could not be determined. The patient also had pulmonary opacities seen on chest radiography. The FDG/PET scan of this patient showed significant extravesical uptake in the pelvis, confirming the abnormality noted on CT. Good images of the clinically apparent metastases in the chest also were obtained. These preliminary data indicate that FDG/PET imaging of bladder cancer is feasible and it may provide new information for the diagnosis and staging of patients with bladder cancer.