Detection of metastases in lymph nodes is an important prognostic factor for progression-free survival in bladder cancer patients. Patients undergoing radical cystectomy with pelvic lymphadenectomy are randomized in the LEA study (AUO AB 25/02) into two groups receiving standard (obturator and external nodes) or extended lymphadenectomy (complete pelvic nodes up to the inferior mesenteric artery).The aim of this study is the detection of lymph node metastases that are not identified with classic pathological methods using RT-PCR as a highly sensitive and specific method. For detection of occult disseminated tumor cells we analyze the expression of the tumor markers cytokeratin 20 (CK-20), uroplakin II (UP II), mucin 2 (MUC2), and mucin 7 (MUC7).We examined 315 lymph nodes from 19 cystectomy patients for the expression of CK-20. In 93 lymph nodes CK-20 expression was detected whereas only 18 lymph nodes were histopathologically positive. More than one third of CK-20-positive lymph node metastases were located outside the standard lymphadenectomy field. We did not detect any skip lesions. Follow-up data will validate if there is a correlation between detection of occult disseminated tumor cells and progression-free survival.