This review paper summarises available information on the Somniosus (sleeper shark) subgenus, comprising three species; S. microcephalus, S. pacificus and S. antarcticus. Taxonomy, distribution, life history, biological characteristics and exploitation by fisheries is discussed. Somniosus antarcticus is caught as by-catch in Australian subantarctic fisheries at Heard and McDonald Islands (Division 58.5.2) and Macquarie Island. Based on present by-catch rates, a risk assessment for this species concluded that there is unlikely to be a serious risk to the stock. A tagging program and continued monitoring of by-catch of this species is ongoing.