ABSTRACT: Seventy-three ostracode species from 38 genera were recovered from the 55 surface sediment samples in Lützow-Holm Bay, northeastern Antarctica. We investigated bathymetric and geographic distributions of modern benthic ostracode species in the bay and compared this fauna with publishedmodern and fossil ostracode data of Antarctic and southern SouthAmerican regions. The results show: (1) Four biotopes and three sub-biotopes are recognized based on Q-mode cluster analysis, which suggest distributions of modern ostracodes are mainly controlled bywater-mass structure, ice scouring, and light availability. (2)Comparison between the Lützow-Holm Bay fauna and other ostracode faunas fromAntarctica and southern SouthAmerica shows high endemism and homogeneity of Antarctic ostracode fauna, suggesting in situ evolution ofmost extant Antarctic species. (3) Most species are endemic to the Antarctica, a few species also inhabit South American waters.