AIM:To explore the relationship between angiogenesis andbiological behaviors of primary gallbladder carcinoma (PGBC),the relationship between the expression of inducible nitricoxide synthase (iNOS) and biological behaviors of PGBC andits relationship with the expression of iNOS and angiogenesisof PGBC.METHODS:The expression of iNOS and micro-vessel density(MVD) were assessed by immunohistochemical method andimage analysis system in 40 specimens of PGBC and in 8specimens of normal gallbladder.The immunostaining resultsand related clinicopathologic materials were analyzed bystatistical methods.RESULTS:MVD in PGBC was significantly higher than thatin normal gallbladder tissue (46±14 vs 14±6,P<0.05),andwas not related with age,gender,tumor size and histologicaltype.MVD of poorly and undifferentiated tumor tissues washigher than that of moderately-differentiated and well-differentiated tumor tissues (52±9 vs 43±9 vs 33±6,P<0.01).MVD of Nevin Ⅳ and Ⅴ stages was higher than that of NevinⅠ,Ⅱ and Ⅲ stages (52±8 vs 37±13,P<0.01).MVD of caseswith lymphatic or liver metastasis was significantly higherthan that without liver metastasis (55±6 vs 42±10,P<0.05)or lymphatic metastasis (53±8 vs 38±8,P<0.01).The positivelevel index (PLI) of iNOS in PGBC was 0.435±0.134,and wasnot related with age,gender,tumor size,histological type,differentiation and clinical stage of PGBC.The PLI of iNOSin cases with lymphatic metastasis was higher than thatwithout lymphatic metastasis (0.573±0.078 vs 0.367±0.064,P<0.01).The PLI of iNOS in cases with liver metastasis washigher than that without liver metastasis (0.533±0.067 vs0.424±0.084,P<0.05).There was a significant correlationbetween PLI of iNOS and MVD in PGBC (P<0.05).CONCLUSION:Angiogenesis of PGBC is significantly relatedto the biological behaviors of PGBC.The expression of iNOSis related to the biological behaviors of PGBC.The detectionof MVD and the expression of iNOS in PGBC can be used asparameters to determine the degree of malignancy and prognosis. AIM: To explore the relationship between angiogenesis andbiological behaviors of primary gallbladder carcinoma (PGBC), the relationship between the expression of inducible nitricoxide synthase (iNOS) and biological behaviors of PGBC andits relationship with the expression of iNOS and angiogenesisof PGBC. METHODS: The expression of iNOS and micro-vessel density (MVD) were assessed by immunohistochemical method and image analysis system in 40 specimens of PGBC and in 8specimens of normal gallbladder.The immunostaining resultsand related clinicopathologic materials were analyzed bystatistical methods .RESULTS: MVD in PGBC was significantly higher than that of normal gallbladder tissue (46 ± 14 vs 14 ± 6, P <0.05), and was not related with age, gender, tumor size and histological type. MVD of poorly and undifferentiated tumor tissues washigher than that of moderately-differentiated and well-differentiated tumor tissues (52 ± 9 vs 43 ± 9 vs 33 ± 6, P <0.01) .MVD of Nevin Ⅳ and Ⅴ stages was higher than that of N (52 ± 8 vs 37 ± 13, P <0.01) .MVD of cases with lymphatic or liver metastasis was significantly higherthan that without liver metastasis (55 ± 6 vs 42 ± 10, P <0.05) or lymphatic metastasis (53 ± 8 vs 38 ± 8, P <0.01). The positivelevel index (PLI) of iNOS in PGBC was 0.435 ± 0.134, and was not related to age, gender, tumor size, histological type, differentiation and clinical stage of PGBC. The PLI of iNOSin cases with lymphatic metastasis was higher than that with lymphatic metastasis (0.573 ± 0.078 vs 0.367 ± 0.064, P <0.01). The PLI of iNOS in cases with liver metastasis washigher than that without liver metastasis (0.533 ± 0.067 vs 0.424 ± 0.084, P <0.05). There was a significant correlation between PLI of iNOS and MVD in PGBC (P <0.05). CONCLUSION: Angiogenesis of PGBC is significantly related to the biological behaviors of PGBC. The expression of iNOSis related to the biological behaviors of PGBC. The detection of MVD and the expression of iNOS in PGBC can be used as parameters the degree of malignancyand prognosis.