This study was carried out to evaluate cytotoxic effects of the roots of Sophora flavescens Ait. extracts on murine leukemia tumor cells lines $(P388D_1;and;L1210)$. Disruptions in cell organelles were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The comparison of $IC_{50}$ values of the ethyl acetate of Sophora flavescens Ait. extract in leukemia cell lines showed that their susceptibility to these extracts decreased in the following order : Adriamycin>Fr.4>Fr.5>Fr.3>Fr.1>Fr.2 by the MTT assay. These results suggest that the fraction 4 of the ethyl acetate soluble extract of Sophora flavescens Ait. may be a valuable choice for the studies on the treatment of murine leukemia cell lines.