This report is a contribution to the Strategic Environmental Assessment (SEA7) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Twenty-one cetacean species have been recorded in the SEA7 region. Of these, ten species are known to occur regularly: harbour porpoise, bottlenose dolphin, short-beaked common dolphin, Risso's dolphin, white-beaked dolphin, Atlantic white-sided dolphin, long-finned pilot whale, killer whale, sperm whale and minke whale. Five further species, though not very often recorded, and primarily associated with deep water, probably also occur regularly: striped dolphins, fin whales, northern bottlenose whales, Cuvier's beaked whale and Sowerby's beaked whale. There are occasional at-sea records of a further 6 species: Sei whale, humpback whale, blue whale, northern right whale and false killer whale. Pygmy sperm whales and at least three further species of beaked whale might also be expected in the general area on occasion. In this report, each of the more abundant species is briefly described with particular reference to its distribution and abundance in the SEA-7 area.