Immunocytochemical techniques have become valuable tools in many fields of clinical pathology and medical research. Especially the development of highly specific (monoclonal) antibodies to a large variety of tissue antigens has in recent years led to the establishment of sensitive tissue markers. One of the most promising types of tissue specific markers so far is represented by the intermediate filament proteins. Since the findings of this rapidly expanding field are also being applied in urology, we have reviewed the current data in order to describe the new insights in tumor biology and histogenesis, as well as their application in diagnostic pathology.