Thirty species of Korean medicinal plants which have been frequently used in Oriental herb prescriptions were evaluated on their acute toxicity and potential antitumor activities against P-388 lymphocytic leukemia. The criteria for toxicity evaluation of measuring weight loss, toxicity day survivors and computing log cell kill indicated that 11 species possessed acute toxicity according to the doses administered. No significant antitumor activities were observed while the root of Angelica gigas Nakai (Umbelliferae) exhibited only 24% increased life span.