Abstract: The drug resistance of the tumor cells is the important factor in the failure of chemotherapy for cancer. To demonstrate the relation between the MDR₁ products and the failure of chemotherapy for bladder cancer, the 72 cases of bladder cancer were studied with the immunohistochemical method. The restults suggested that the positive rate and the strong positive rate of the MDR₁ products in the cases, in which the chemotherapy with mitomycin pouring into the bladdler post-operation was fail, were higher than those in the initial stage of bladder cancer. The positive and strong positive expressions of MDR₁ products in the high differentiation tumors were higher than those in the low differentiation tumors. This research indicated that the outcome of the chemotherapy for bladder cancer is relevant to the amounts of the MDR₁ products in the bladder cancer tissue.

Key words: bladder cancer, MDR₁ gene, P-GP₁₇₀ glycoprotein, immunohistochemical method, the chemotherapy in the bladder