BACKGROUND: Little is known about the mechanisms of arsenic-related urothelial cancer (AsUC). The aim of this study was to reveal the differential expression of molecular markers between AsUC and non-arsenic-related UC (non-AsUC). MATERIALS AND METHODS: Tissues of AsUC (n=33), non-AsUC (n=20) and normal bladder urothelia from patients with benign diseases (n=4) were examined for multiple selected molecular markers responsible for various cellular functions, includingglutathione, GST-pi, Bcl-2, p53 and c-Fos. RESULTS: The mean cellular glutathione content of normal mucosal samples (33.4 +/- 7.2 microM/mg protein) was significantly higher than either non-AsUC (22.8 +/- 1.8, p = 0.04) or AsUC (16.4 +/- 1.6, p = 0.002). The glutathione content of non-AsUC was higher than that of AsUC (p = 0.012). The expressions of Bcl-2 and c-Fos in AsUC were significantly higher than those in non-AsUC (p = 0.004 and p = 0.02, respectively). CONCLUSION: The carcinogenic pathway for AsUC is different, in part, from that of non-AsUC. Cellular glutathione contents may be down-regulated during urothelial carcinogenesis. Bcl-2 and c-Fos may play important roles in arsenic-mediated carcinogenesis of the urothelium.