This study was carried out to obtain basic data for alien plant management in South Korea. Field surveys were conducted in forests, fields, islands, industrial complexes, landfill areas, and so forth from 1995 to 2002. The number of naturalized alien plants recorded in Korea was 39 families and 281 taxa through 2002. Members of the Asteraceae and Poaceae families were the most frequently growing alien plants in Korea and comprise 23 and 17% of the total population, respectively. Most of them invaded South Korea from Europe and North America. Ministry of Environment in Korea designated six alien plants as harmful nonindigenous plants on ecosystems by the Natural Environment Conservation Act, considering their possible negative effect on the ecosystem. Those species were ragweed, giant ragweed, white snakeroot, joint grass, knotgrass, and horsenettle. On the basis of the research, we constructed a database titled An Illustrated Internet Guide to Alien Plants in Korea ( http://alienplant.nier.go.kr). We expect the database to help increase public awareness and encourage citizens to participate in the management of alien plants.

Nomenclature: Giant ragweed, Ambrosia trifida; horsenettle, Solanum carolinense L.; joint grass, Paspalum distichum var. distichum L.; knotgrass, Paspalum distichum var. indutum; Shinners ragweed, Ambrosia artemisiifolia var. elatior (L.) Desc.; white snakeroot, Eupatorium rugosum Houtt.

Additional index words: Alien plants, database, harmful nonindigenous plant.