The Eastern Arc Mountains are renown in Africa for high concentrations of endemic Received 17 June 2005 species of animals and plants. Thirteen separate mountain blocks comprise the Eastern Received in revised Arc, supporting around 3300 km 2 of sub-montane, montane and upper montane forest, less form 29 June 2006 than 30% of the estimated original forested area. At least 96 vertebrate species are endemic, Accepted 8 August 2006 split as follows: 10 mammal, 19 bird, 29 reptile and 38 amphibian species. This includes Available online 12 October 2006 four endemic or nearly endemic species of primate – the Sanje Mangabey, the Iringa Red Colobus, the Mountain Galago and the new Kipunji monkey that forms its own monotypic Keywords: genus. A further 71 vertebrate species are near-endemic. At least 800 vascular plant species Biodiversity conservation are endemic, almost 10% of these being trees. These endemics include the majority of the Eastern Arc Mountains species of African violet – Saintpaulia, a well-known flowering plant in Western households. Protected areas An additional 32 species of bryophytes are also endemic. Many hundreds of invertebrates Diversity are also likely to be endemic, with data for butterflies, millipedes and dragonflies indicating Endemism potential trends in importance. Seventy-one of the endemic or near-endemic vertebrates are threatened by extinction (8 critical, 27 endangered, 36 vulnerable), with an additional seven wide ranging threatened species. Hundreds of plant species are also threatened