To examine the allelopathic potentials of Chrysanthemum boreale, aqueous extracts and essential oil of the plant were used in these experiments. Seed germination of the receptor species was inhibited by the aqueous extracts and the inhibitory effect was increased in proportion to the concentration of extracts. In contrast, seedling elongation showed varied results. Achyranthes japonica, Bidens bipinnata, Raphanus sativus var. hortensis for. acanthiformis, Plantago asiatica, Pimpinella brachycarpa and Lactuca sativa were inhibited by increasing concentration of the aqueous extract, while Brassica campestris subsp. napus var. pekinensis and Echinochloa crus-galli were stimulated by the extract. Dry weight was also inhibited proportionally by increasing concentration of the aqueous extract, while some species were stimulated by a lower concentration of the extract. The volatile substances of C. boreale did not affect the seed germination of receptor plants, but seedling elongation and dry weight of some species were inhibited dose-dependently. Root hair development of selected plants was inhibited along with the concentration of essential oil. The above mentioned results, therefore, confirmed that the natural substances from C. boreale had allelopathic potentials to other plants.