This working paper provides a global overview of the current coverage of existing World Heritage Sites of particular importance for the conservation of biodiversity, and suggests existing protected areas of significant biodiversity value, which may merit future World Heritage nomination. In 1996, IUCN initiated a project to prepare a global strategy for Natural World Heritage sites, and as part of this process began to prepare a series of thematic global overviews on World Heritage site coverage. This document is an updated addition to these theme studies. A total of 141 sites, representing 64 countries and over 142 million ha of protected areas were identified as being of particular importance for biodiversity. The sites detailed in this study were selected on the basis of natural World Heritage sites that lay within or contained a site that had been defined.