In order to examine the suitability of leukocyte migration inhibition test (LMIT) in the capacity of in vitro assay system for dialyzable leukocyte extracts (DLE), the effect of DLE on hepatitis B and its antigen-specificity, the migration inhibitory activities to purified hepatitis B surface antigen (HBsAg) was measured using the leukocyte MIF test with DLEs obtained from HBsAb-positive or HBsAb-negative blood. The direct LMIT using agarose plate was modified according to the technique of Clausen et al. In spite of our assay system was dose-dependent for PPD, a significant response for purified HBsAg was not observed. However, some meaningful migration inhibition appeared when HBsAg and DLE were added simultaneously to the migration cells. From these results, it is concluded that DLE has antigen-specific and/or antigen non specific influences to the cell-mediated immunity for HBsAg Though some problems remain, we think our results are interesting, since the assay system for DLE has not been established and our study is closely related to the effect of DLE concerning hepatitis B.