The National Institute Agricultural and Science Technology, the National Crop Experiment Station, the National Honam Agricultural Experiment Station and the National Yeongnam Agricultural Experiment Station did Paddy weed survey from 2000 to 2001. Weeds of paddy rice fields are composed of 76 species belonging to 22 families. Dominance by family is 11.8%, 20.4%, and 12.8% in Poaceae, Cyperaceae and Pontederiaceae, respectively. Dominance by species is 12.7%, 9.5%, 9.5%, and 9.1% in Monochoria vaginalis, Eleocharis kuroguwai, Echinochloa spp., and Sagittaria trifolia, respectively in decreasing order. Annual broadleaf weeds and perennial are widely distributed. Annual weeds showed high dominance of 70% compared with perennials weeds. Dominant weeds occurring in different cultivation methods are Echinochloa spp. in direct seeded paddy fields and Rindernia procumbens and Monochoria vaginalis in double cropping paddy fields after barley cultivation. The current survey indicated that annual weeds such as Monochoria vaginalis and Echinochloa spp. were widely distributed and perennial weeds have greatly increased for the last 10 years