The author of this analytical review of the recently published revision of the Mammals Red Data Book has been a member of the Survival Service Commission (SSC) of the International Union for Conservation of Nature and Natural Resources (IUCN) since 1963, and is one of the five members of the small advisory Alert Group within the Commission. A widely known naturalist and anthropologist, he spent 22 years in Borneo, where he was deeply involved in South-east Asian conservation problems. He also initiated, planned and carried out with General Charles Lindbergh one of the SSC's most successful projects—a two-man mission which persuaded the Philippines Government to act to save the tamaraw, described in Oryx 1969, pages 8 and 87. The SSC is officially responsible for the Red Data Books, the idea for the series being the invention of the chairman, Sir Peter Scott. There are now five volumes: Mammals, Birds, Amphibia and Reptiles, Freshwater Fish and Angiosperms.