Abstract : The Anopheles Hyrcanus Group consists of several species that are vectors of malaria and other mosquito-borne diseases in the Oriental and Palearctic Regions. The group has about three-quarters of the species that comprise the Myzorhynchus Series of genus Anopheles Meigen subgenus Anopheles in the two regions. It has about 30 species, including two newly described species, An. belenrae Rueda and An. kleini Rueda (Rueda 2005). In South Korea (Republic of Korea), there are only six known species of the Hyrcanus Group. Le., An. sinensis Wiedemann, An. sineroides S.Yamada, An. lesteri Baisas and Hu, An. pullus M.Yamada (Tanaka et al. 1979), and An. belenrae and An. kleini (Rueda 2005). Other non-Hyrcanus Group species of Anopheles (Anopheles) in South Korea are An. koreicus Yamaha and Watanabe and An. lindesayi japonicus S.Yamada (Tanaka et al. 1979). Because of the limited information about the distribution and larval habitat characteristics of the Hyrcanus Group and its associated species, we conducted this study from 1998-2004 in South Korea. Anopheles sinensis is considered the most common Anopheles species in South Korea (Chai 1999), but its distribution within Korea is not well documented, except in Jeju Province (Kim et al. 2005a). In China, Rueda et al. (2005a) noted the occurrence of this species in eight provinces and one city (Beijing). Adults of An. sinensis have been incriminated as the natural and/or experimental malaria (Plasmodium vivax) vectors in South Korea (Lee et al. 2002), Japan (Otsuru and Ohmori 1960), China (Ho et al. 1962) and Indonesia (O'Connor 1980). Although it is found in Thailand, All. sinensis has minimal or no importance as a malaria vector in that country (Harrison and Scanlon 1975). In South Korea, it was found to be the major vector involved in the transmission of P. vivax along the border with North Korea since 1993 (Ree et al. 2001, Kim ct al. 2005b).