PET is a new method in nuclear medicine which examines the metabolism and not the morphology. Tumors show a higher rate of glycolysis than benign tissue and hence can be detected by radioactive glucose. This method has proved good for various tumors. In this study the lymph node staging of bladder cancer by PET was investigated. In 64 patients a PET of the pelvis after injection of fluorodeoxyglucose (FDG) was carried out preoperatively; the PET-results were compared with the histology of the OR specimen after classical pelvic lymphadenectomy. For lymph node staging positive nodes were found in 14 patients which was correct; a false-negative result was obtained in 7 patients. In 37 patients the PET-result was true-negative and in 6 patients false-positive resulting in a sensitivity of 67%, a specificity of 86% and an accuracy of 80%. Therefore, our PET results are encouraging and seem to be better than those obtained by classical staging procedures such as CT or MRI.