The precise timing of the angiogenic switch in colorectal cancer development is still unclear. The simultaneous expression of Endoglin (CD105), transforming growth factor (TGF)-β1 and TGF-β receptor (R) II were quantified in surgical specimens comprising normal human colon, pre-malignant dysplastic tissue, in situ, and invasive colon cancer specimens, at mRNA and protein levels, respectively by real-time PCR and immunohistochemistry. Serum concentrations of soluble Endoglin and TGF-β1 were evaluated. mRNA and CD105+-microvessel density (MVD) increased significantly in dysplastic colon and carcinoma versus normal tissues; values correlated respectively with dysplasia degree and Dukes' stages. TGF-β1 expression was significantly upregulated in most severe dysplastic adenoma specimens, while TGF-β1 transcript and protein signals were intense in carcinoma, positively-correlated with tumor progression. TGF-β1 RII was overexpressed in adenoma and carcinoma versus normal samples, but unrelated with dysplasia or Dukes' stage. Soluble Endoglin serum levels were equivalent in adenoma and normal tissues; in carcinoma the highest levels were in invasive tumor. Circulating TGF-β1 levels were increased in severe dysplasia and progressed with tumor progression. Correlations between adenoma dysplasia degree and TGF-β RII and CD105+-MVD, and between tumor Dukes' staging and TGF-β1 and CD105+-MVD, were significant. TGF-β1 and Endoglin and TGF-β1 serum levels, TGF-β1 staining and CD105+-MVD were significantly and inversely associated with disease-free survival. TGF-β1 levels were an independent and significant prognostic factor of disease-free survival. These findings suggest active angiogenesis occurs in many pre-malignant colon cases and supports more careful evaluation of different chemopreventive agents.