We evaluated the possible correlation between intracellular glutathione (GSH) and drug sensitivity of urothelial cancer. Tissue GSH content of surgical specimens from 20 patients with urothelial cancer was assayed with high performance liquid chromatography (HPLC). GSH levels of cancer tissue (7.887 +/- 6.176 microM/mg protein) were significantly higher than GSH levels of normal mucosa (1.345 +/- 1.252 microM/mg). All patients having measurable lesions were then treated with methotrexate, epirubicin and cisplatin (MEC). These patients were classified into three groups according to clinical response criteria. GSH content in cancer tissue from four patients with complete response was 0.804 +/- 1.183 microM/mg protein. However, the cancer cells from patients with partial response and non-response contained a significantly higher level of GSH (6.295 +/- 2.459 (n = 8) and 12.955 +/- 6.141 microM/mg protein (n = 8), respectively). Intracellular glutathione content may play an important role in intrinsic resistance of urothelial cancer to MEC chemotherapy. It might be potentially used to predict drug sensitivity in urothelial cancer patients before starting chemotherapy.