AIM:Angiogenesis is an important step in the growth ofsolid malignant tumors.A number of angiogenic factors havebeen found such as transforming growth factorβ1(TGF-β1)and vascular endothelial growth factor(VEGF).However,the roles of TGFβ1 and VEGF in gastrointestinalcarcinogenesis are still unclear.This study was to investigatethe expressions of TGF-β1 and VEGF in gastrointestinal tractmalignant tumors,as well as their association withmicrovessel density(MVD).At the same time,we alsoobserved the localization of TGF-β1 and its receptor CD105in gastric malignant tumors.METHODS:The expressions of TGF-β1 and CD105 weredetected in 55 fresh specimens of gastric carcinoma andVEGF and CD105 in 44 fresh specimens of colorectalcarcinoma by immunohistochemical staining(S-ABC).TGF-β1and CD105 in 55 gastric carcinoma tissues on the same slidewere detected by using double-stain Immunohistochemistry(DS-ABC).RESULTS:Among the 55 cases of gastric carcinoma tissues,30 were positive for TGF-β1(54.55 %).The MVD of TGF-β1strong positive group(++～+++ 23.22±5.8)was significantlyhigher than that of weak positive group(+17.56±7.2)andnegative group(-17.46±3.9)(q=4.5,q=5.3207,respectively,P<0.01).In the areas of high expression of TGF-β1,MVDand the expression of CD105 were also high.Among the 44cases of colonic carcinoma tissues,26 were positive for VEGF(59.1%).The expressions of both VEGF and CD105(MVD)were related with the depth of invasion(F=5.438,P<0.05;F=4.168,P=0.05),lymph node metastasis(F=10.311,P<0.01;F=20.282,P<0.01)and Dukes stage(F=6.196,P<0.01;F=10.274,P<0.01),but not with histological grade(F=0.487,P>0.05).There was a significant correlation between theexpression of VEGF and CD105(MVD)(r=0.720,P<0.01).CONCLUSION: Over-expression of TGF-p1 and VEGF acts as stimulating factors of angiogenesis in gastrointestinal tumors. CD105, as a receptor of TGF-p1, can regulate the biological effect of TGF-p1 in tumor angiogenesis. MVD marked by CD105 is more suitable for detecting newborn blood vessels. AIM: Angiogenesis is an important step in the growth of solid malignant tumors. A number of angiogenic factors have found such as transforming growth factor β1 (TGF-β1) and vascular endothelial growth factor (VEGF). The roles of TGFβ1 and VEGF in gastrointestinal carcinogenesis are still unclear. This study was to investigate the expressions of TGF-β1 and VEGF in gastrointestinal tract malignant tumors, as well as their association with microvessel density (MVD). At the same time, we alsoobserved the localization of TGF-β1 and its receptor CD105 in gastric malignant tumors. METHODS: The expressions of TGF-β1 and CD105 weredetected in 55 fresh specimens of gastric carcinoma and VEGF and CD105 in 44 fresh specimens of colorectalcarcinoma by immunohistochemical staining (S-ABC). TGF-β1 and CD105 in 55 gastric carcinoma tissues on the same slidewere detected by using double-stain Immunohistochemistry (DS-ABC) .RESULTS: Among the 55 cases of gastric carcinoma tissues, 30 were positive for TGF-β1 (54 .55%). The MVD of TGF-β1strong positive group (++ ~ +++ 23.22 ± 5.8) was significantlyhigher than that of weak positive group (± 17.56 ± 7.2) and negative group (-17.46 ± 3.9) (q = 4.5 , q = 5.3207, respectively, P <0.01) .In the areas of high expression of TGF-β1, MVD and the expression of CD105 were also high.Among the 44cases of colonic carcinoma tissues, 26 were positive for VEGF (59.1%). The expressions of both VEGF and CD105 were associated with the depth of invasion (F = 5.438, P <0.05; F = 4.168, P = 0.05) , P <0.01) and Dukes stage (F = 6.196, P <0.01; F = 10.274, P <0.01), but not with histological grade and CD105 (MVD) (r = 0.720, P <0.01) .CONCLUSION: Over-expression of TGF-p1 and VEGF acts as stimulating factors of angiogenesis in gastrointestinal tumors. CD105, as a receptor of TGF-p1, can regulate the biological effect of TGF-p1 in tumor angiogenesis. MVD marked by CD105 is more suitable for detecti ng newborn blood vessels.