Up to now markers for transitional cell carcinoma of the bladder (TCC) are missing. Fibronectin (FN) seems to play a key role in progression and invasion of malignant tumors. The aim of this study was to assess the value of cellular FN (cFN), a more specific subform of produced FN, in different stages of TCC.cFN was determined using a highly sensitive immunoassay which we developed. Blood samples were taken of 45 patients with the first diagnosis of TCC before undergoing TUR-B and 6 patients with metastatic TCC before chemotherapy; 70 patients with nonmalignant urological disorders served as a control group.Patients with TCC showed significantly elevated cFN plasma levels compared to controls (p<0.05). Patients with muscle-invasive disease (n=15) showed significantly higher cFN plasma levels compared to the group with superficial TCC. Patients with metastatic TCC showed the highest, but not significantly elevated cFN plasma levels compared to patients with muscle-invasive TCC.The elevated cFN plasma levels in TCC underline the important role of cFN for tumor progression and its potential role as a marker for TCC. Upcoming investigations are necessary to prove the value of the potential marker cFN during follow-up and its impact as a prognostic factor for recurrence and progression of TCC.