Amplification of the c-erbB-2 oncogene and protein overexpression are well-known in breast cancer and a basis for therapy with the monoclonal antibody trastuzumab, which binds to the receptor encoded by c-erbB-2. Regarding bladder carcinoma, several studies have examined c-erbB-2 expression, but their results are quite heterogeneous. In the present study, we evaluated the expression of this oncoprotein immunohistochemically in 203 muscle-invasive urothelial bladder carcinomas using the HercepTest. Additionally, 42 cases were studied for gene amplification by fluorescence in situ hybridization (FISH) using the PathVysion kit. Follow-up was known in 147 patients. The results were compared with pathologic characteristics and disease-related survival. Immunohistochemical c-erbB-2 overexpression was observed in 37% of the tumors (76/203). However, only 5% (2/42) showed amplification of the oncogene, indicating that predominantly other mechanisms than gene amplification may cause protein overexpression in bladder cancer. C-erbB-2 protein overexpression was significantly associated with high tumor grade (p=0.004) and infiltrative growth pattern (p=0.0001), and tendentiously associated with the presence of lymph node metastases (p=0.077). Regarding tumor stage, sex and age, no significant correlation was registered. Kaplan-Meier curves showed a significantly worse disease-related survival for patients with c-erbB-2 overexpressing tumors (p=0.0346 by log-rank test). Multivariate analysis revealed that, besides nodal status (p=0.0001) and tumor stage (p=0.028), c-erbB-2 overexpression was an independent predictor of disease-related survival (p=0.030). Thus, our results suggest that immunohistochemical c-erbB-2 detection might represent an additional tool in determining bladder cancer prognosis. Clinical trials evaluating the efficacy of trastuzumab therapy in bladder cancer patients are warranted.