It is generally accepted that there are dichotomous biologic pathways that lead to the development of either: i) superficial papillary (Ta) transitional cell carcinoma (TCC) or ii) precursor lesions to muscle-invasive (CIS, T1) TCC and muscle-invasive (> or =T2) TCC. We investigated the expression of several progression-related genes to characterize the phenotype of these tumors within these divergent developmental pathways. Using a colorimetric in situ hybridization technique, we examined the expression of mRNAs of several progression-related genes in archival, pathologic specimens from 77 patients with bladder TCC. These genes included basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), interleukin (IL)-8, matrix metalloproteinase (MMP)-9, and epidermal growth factor receptor (EGFR). Relative gene expression was quantified using image analysis. Gene expression was normalized using poly (dT) and the expression of each factor in a panel of specimens of normal urothelium. Patients were stratified according to disease stage, and the level of gene expression among the stratified groups was compared. VEGF, bFGF, IL-8, and MMP-9 expression was increased in muscle-invasive compared with superficial papillary tumors, (p<0.05) and VEGF expression was increased in muscle-invasive tumors compared with CIS specimens (p<0. 05). bFGF, IL-8, and EGFR expression was increased in CIS specimens compared with superficial papillary tumors (p<0.05). The pattern of expression of bFGF, VEGF, IL-8, MMP-9, and EGFR represent the divergent developmental pathways in the pathogenesis of bladder TCC, which characterizes superficial or invasive bladder cancer. bFGF, IL-8, and EGFR appear to be upregulated in early precursor lesions (CIS), whereas VEGF appears to be upregulated at later stages in the development of muscle-invasive TCC.