During the past fifty years, there had been a great deal of interest in screening therapeutic agents from plants. Bidens pilosa L. is widely used in traditional medicine for antiinfluenza, diabetic control and treatment of gastroenteritis. Houttuynia cordata Thunb. is used in traditional Chinese medicine for treating infectious disease, refractory hemoptysis, malignant pleural effusion and nephrotic syndromes. Studies have shown that B. pilosa possessed anti-hyperglycemic, Anti-ulcerogenic, immuno-suppressive, anti-inflammatory, vaso-dilative, hypotensive, anti-malarial, anti-bacterial and hepato-protective activities. But also co-carcinogenesis and photo-cytotoxicity were reported with different species of B. pilosa. H. cordata has biologic activities including anti-microbial, anti-viral immunostimulatory, diuretic, anti-cancer, sedative, anti-inflammatory and antitussive effects. Although H. cordata was reported to be active against ascitic tumor, it was unknown whether hot water extracts (HW) of B. pilosa var. minor or H. cordata had anti-leukemic activity. In searching natural crude drugs for potential anti-leukemic activity, we tested whole plant HW extracts of B. pilosa var. minor and H. cordata.