For the research of cytotoxic natural products, 50 medicinal plants were extracted with benzene and methanol, separately, and screened against L1210 cells. From the results(Table I), 6 samples showed cytotoxicity both in benzene and methanol extracts of 17 samples in benzene extracts and 3 samples in methanol extracts, respectively. Generally, the cytotoxicity exhibited high frequency (34%) in benzene extract but low frequency in methanol extract (6%), it meant that active cytotoxic components had less polarity. $ED_{50}$ values less than $10;{mu}g/ml$ were observed in 17 medicinal plants.