Abstract: The distribution of different type of trophoblast in 91 malignant trophoblastic neoplasms was studied immunohistochemically using a panel of antibodies against cytokeratin(CK),hCG and hPL.The results showed that the trophoblastic component was different between invasive mole and chorio carcinoma. Although there was numerous syncytiotrophoblast (ST)in both, but the number of intermediate trophoblast (IT) in invasive mole was much more than one in choriocarcinoma, the number of cytorophoblast (CT) in the latter was far more than one in the former. For invasive mole,the discrepancy at cellular component metastatic and primary was not obvious. But for choricocarcinoma, the uumber of ST in metastatic far more than on in primary,the number of CT in the formerwas much less than one in the latter, the number of IT in both did not exhibit evident difference. Webelieved that the role of ST in malignant trophoblastic neoplasms could merit further research.