The expression of P- glycoprotein was detected in 47 cases of untreated head and neck cancer using immunohistochemical ABC method.For comparative purposes.the chemosensitivity tests in vitro to eight kinds of antineoplastic drugs were performed in 43 cases of tumor by means of argyrophilic staining of nucleolar organizer regions (AgNOR).The results showed that the total positive staining of P-glycoprntein was 57% .The chemotsensitivities to VCR
ADM
PYM
MMC in the group of P-glycoprotein positive staining were significantly lower than those in the group of P-glycoprotein negative staining(P<0.05).The results indicate that P-glycoprotein expressing spontaneously in head and neck cancer is assnciated with intrinsic clinical multidrug resistance.