Standardized short DNA sequences of the genome provide a DNA barcode for identifying species. Assembling DNA barcode data of regional fauna could provide a new identifying system and it will aid regional and global taxonomic studies and other applied biology. Recently, partial cytochrome c oxidase I (COI) sequences, around 670-bp region of the mitochondrial gene, has been qualified as a good DNA barcode for the identification of insect species. The superfamily Nepoidea includes two families-Belostomatidae and Nepidae. And it contains about 377 species in 23 genera worldwide. In Korea, each family is recognized 4 species 3 genera, respectively. As a part of the Korean insect DNA barcode project, we conducted preliminary DNA barcode study on Korean Nepoidea to provide useful molecular data for aiding accurate identification. This study also tested the effectiveness of a COI barcode in discriminating Korean Nepoidea species. So far, 43 individuals of 8 species belonging to two families were analyzed. We used a 658-bp fragment of COI gene was sequenced. Pairwise sequence divergences were calculated using a Kimura 2-parameter model and constructed neighbor-joining tree to calculate generic differences among species and within species.