With the development of neuroimagine and further understanding of the etiology of the cerebral cavernous malformation (CCM) , the importance of CCM is gradually being realized by clinicians. Now, CCM have become one of the major cerebravascular diseases, directly threatening human lives and health. At present, the CCM keep many unknowns to us in the experimental field .To further explore the pathogenesis of CCM and the potential for the optimal treatments for the disease , the research has been carried out through the study of biological and genetic characters of the CCM. Part I. The pathological and immunohistochemical study on the CCM Objective To explore the histological structure,angiogenesis and proliferative activity of CCM and to explore the relation between the clinical presentations and pathological characteristics of CCM by pathological and immunohistochemical study . Methods 70 surgical samples of CCM and 20 normal control brain tissue samples were stained with routine HE and immunohistochemically with CD34、SMA;VEGF、Flt-1;TGFa、Ki67 respectively. A comparison analysis was made according to the expression intensity. All the CCM samples were further divided into intra- and extra-cerebral groups for another comparison analysis. Results All the normal control brain tissue expressed obvious and continuous positive staining of CD34 and SMA ,but negative staining of VEGF, Flt-1 or TGFa . By contrast,47 and 50 of 70 CCM were stained positive for CD34 and SMA respectively,and the expression demonstrated less continuous. 68 and 44 CCM were stained positive for VEGF and Flt-1 respectively with diffuse distribution. 68 CCM were stained positive for TGFa. there was significant difference in expression intensity of above 5 factors between the normal control brain tissue and CCM(P<0.05).No expression of Ki67 was detected in all samples. The extracerebral CCM group,completely different from the intracerebral one, presented elastic and thick-wall vessel. Conclusion The biological characteristics of the CCM are mainly relevant to the unmaturity of the vessel wall. A series of angiogenic factors play an important role in the development of the lesion. The proliferative activity of the CCM needs to be studied further. The different clinical presentations of CCM was based on its pathological diversity.