This book represents the most comprehensive compilation of data on threatened vascular plants ever published. It includes the names of some 33,000 plant species determined to be rare or threatened on a global scale. Conservation assessments were provided by the IUCN Species Survival Commission, the National Botanical Institute (South Africa), Environment Australia, and CSIRO, The Nature Conservancy, the Smithsonian Institution, and the Royal Botanic Gardens, Kew, together with hundreds of botanic gardens and botanists throughout the world. The Royal Botanic Gardens Edinburgh and the New York Botanical Garden have made major in-kind contributions. The result of 20 years work by botanists and conservationists around the world, it is intended as a conservation tool, a provider of baseline information to measure conservation progress and as a primary source of data on plant species. Most importantly, however, it provides the building blocks on which to base a worldwide effort to conserve plant species.