An international consultation on the diagnosis of non-invasive urothelial neoplasms was held in Ancona, Italy in May 2001. Besides histology and problems of classification, one group of experts (Committee no. 3) discussed the molecular pathology and cytometry of non-invasive urothelial carcinomas. In the following first part, special immunohistochemical and molecular markers for stratifications in bladder cancer were discussed including different cytokeratins (clone 34betaE12, CK 20), cell proliferation markers (Ki67/MIB-1, PCNA, AgNOR, DNA-cytometry), tumor suppressor genes and oncogenes (p53, p21, erb-B2, bcl-2), different receptor expressions of epidermal growth factor and vascular endothelial growth factor and others. These molecular markers were analyzed in diagnosis of urothelial carcinomas, recurrences, progression and response to treatment.