Materials used in this work were collected during BIOM ASS - SIBEX project in the Drake Passage and the Bransfield Strait (1983/1984) in three water layers: 0 - 100 m, 100 — 300 m and 300—500 m. Four species of Chaetognatha were found: Eukrohnia hamata and Sagitta gazellae in both water regions; Sagitta planctonis occurred mainly in the Drake Passage whereas Sagitta marri was noted in the Bransfield Strait and adjacent parts of the Bellingshausen and Scotia seas. Chaetognatha were most numerous in the Drake Passage and generally in the layer 100 — 300 m. Vertical distribution of Chaetognatha was clearly influenced hydrological conditions.