SD-994 was prepared from methanol extract of Artemisia argyi by stepwise purification of solvent partioning and silica gel chromatography. In the course of this purification, fractions obtained at each step were investigated for their cytotoxicities against L1210 cells. Fractions A~G prepared from chloroform fraction showed considerable cytotoxicities raging 40~90% against L1210 cells. Subfractions I~IX obtained from fraction A exhibited various cytotoxicities and subfraction I (SD-994) was found to be the most effective compound. $IC_{50}$ values of SD-994 were measured to be $0.5{;}{mu extrm{g}}/ml and less than $0.05{;}{mu extrm{g}}/ml against L1210 cells and normal lymphocytes, respectively: When SD-994 was added to L1210 cell as cytotoxic agent, significantly increased amount of superoxide ($O_2^-$) and dramatically augmented activities of superoxide dismutase (SOD), specially MnSOD and glutathione peroxidase (GPx) were observed according to the concentration and incubation time. Whereas, in case of normal lymphocytes under the same condition, cytotoxicities were not apparent and the generation of superoxide ($O_2^-$) or the activity changes of SOD and GPx were insignificant. These results together indicate that the cytotoxic action of SD-994 against L1210 cell may be achieved via necrosis and/or apoptosis induced by reaction oxygen species which could not probably be completely abolished even by drastically increased antioxidant enzymes, SOD and GPx activities.