Fiftythree species(35 families and 52 genera)of Korean medicinal plants which have been frequently used in oriental herb prescriptions or have been used as folklorics were evaluated on their short term acute toxicity and potential antitumor activities against P-388 murine lymphocytic leukemia model in vivo. Among these plants Acorus gramineus (Araceae), Agrimonia pilosa (Rosaceae), Aralia elata (Araliaceae), Dryopteris crassirhizoma (Aspidiaceae), Syringa reticulata (Oleaceae) and Calystegia japonica (Convolvulaceae) exhibited potent acute toxicity resulting from severe weight loss and death. Agrimonia pilosa (Rosaceae) showed about 33% of increased life span in comparison with that of control group mouse, but others exhibited no significant antitumor activities.