The distribution pattern and affinities of nearly 7 genera and 11 species of fish-leeches known from the southern Indian Ocean and 8 genera and 10 species from the Antarctic are examined. It is noted that there is great paucity of records of fish-leeches from the southern Indian Ocean, but nevertheless, those known, show a very much restricted distribution at the species level. But at the generic level, the fish-leeches of the southern Indian Ocean show affinities with the tropical and subtropical forms on one side and with the Antarctic forms on the other. The Antarctic forms in turn, show affinities with the Arctic forms besides including some unique genera unrepresented elsewhere in the world.