Specimens of Bosmina longirostris collected from various freshwater habitats of 84 localities in South Korea from October 1981 to August 1997 were examined, and seasonal changes of the cladoceran populations in Late Kwangjuho from October 1995 to August 1977 were analysed. In this paper, B. longirostris in Korea was redescribed and figured, with a discussion of morphological characteristics. Some ecological features of the species were noted.