Purpose　The aim is to prepare the extract of immunocompetent cell proliferation from human placenta and to try to find out a suitable method of preserving the extract.Methods　The extract was mainly prepared by heat-treating placenta homogenated fluid. Then the activity to stimulate murine splenic lymphocyte proliferation in vitro was done with MTT , exposing　the　extract to　radioisotope 60　Co.Results　The content of protein was 2～3mg per gram placenta measured by Lowry′s Method.The rate to promote cell proliferation was more than 80 percent.The activity lasted a few months after being exposed to radioisotope.Conclusion　The extract prepared by heat-treating not only had high activity, but also had the unique method and good repeatability.This prepared extract as a kind of stable,reliable and remarkably promoting lymphocyte proliferation reaction had the value of development production on broad scale as well as in clinical practice.