AIM:To investigate the relationship between the expressionof P-glycoprotein(P-gp)and the degree of vascularizationin gallbladder carcinomas.METHODS:P-gp was stained with streptavidin-peroxidasecomplex immunohistochemical method in routine paraffin-embedded sections of gallbladder carcinomas.Microvesselcounts(MVC)were determined using factor-Ⅷ-relatedantigens.RESULTS:The average MVC in 32 cases of gallbladdercarcinomas was(34±10)/HP.The value of MVC was closelycorrelated with Nevin staging and tumor differentiation(P<0.01 and P<0.05).The total expression rate of P-gpwas 62.5 %.The P-gp expression rate in cases of Nevinstaging S1-S3(78.6 %)was higher than that of S4-S5(50.0 %)with no statistical significance.The P-gp expressionrate was not correlated with tumor differentiation orpathologic types.The value of MVC in P-gp(+)cases wasmarkedly lower than that in P-gp(-)cases(P<0.01).Thepositive rate of P-gp was significantly higher in cases ofsmaller MVC than those of bigger MVC(P<0.05).CONCLUSION: MVC may be used as one of the important parameters to reflect the biological behaviors of gallbladder carcinomas. As a major cause of drug resistance, the overexpression of P-gp is closely correlated with the poorvascularization in gallbladder carcinomas. AIM: To investigate the relationship between the expression of P-glycoprotein (P-gp) and the degree of vascularization in gallbladder carcinomas. METHODS: P-gp was stained with streptavidin-peroxidase complex immunohistochemical method in routine paraffin-embedded sections of gallbladder carcinomas. Microvesselcounts MVC) were determined using factor-VIII-related antigens. RESULTS: The average MVC in 32 cases of gallbladder carcinomas was (34 ± 10) / HP.The value of MVC was closelycorrelated with Nevin staging and tumor differentiation (P <0.01 and P <0.05 ). The total expression rate of P-gpwas 62.5%. The P-gp expression rate in cases of Nevinstaging S1-S3 (78.6%) was higher than that of S4- S5 (50.0%) with no statistical significance.The P- gp expressionrate was not correlated with tumor differentiation orpathologic types.The value of MVC in P-gp (+) cases wasmarkedly lower than that in P-gp (-) cases (P <0.01). in cases ofsmaller MVC than those of bigger MVC (P <0.05) .C ONCLUSION: MVC may be used as one of the important parameters to reflect the biological behaviors of gallbladder carcinomas. The major cause of drug resistance, the overexpression of P-gp is closely correlated with the poorvascularization in gallbladder carcinomas.