Growth and DNA synthesis inhibitory effects of extracts from root bark of Ulmus parvifolia on MG-63 human osteosarcoma cells, HT-29 human colon cancer cells and K-562 leukemia cancer cells were studied. The root bark extract of Ulmus parvifolia was extracted with methanol, hot water and juice. The methanol extract showed the highest inhibitory effect on growth of MG-63, HT-29 and K-562 cancer cells by >85%. The treatment of hot water and juice extracts from root bark of Ulmus parvifolia also inhibited growth of the above cancer cells with increasing concentration. DNA synthesis of MG-63 and HT-29 cancer cells was significantly inhibited by adding methanol, hot water and juice extracts from root bark of Ulmus parvifolia with increasing concentration, showing that the inhibitory effect of growth was more effective on HT-29 cancer cells. These results suggest that the methanol extract from root bark of Ulmus parvifolia may have specific active com-pounds on anticancer effect. The hot water extract also showed a strong inhibitory effect on growth of cancer cells, indicating that the active compounds may be stable to heat.