Madagascar is a critical priority for international conservation efforts, based on almost unparalleled levels of endemism, species diversity, and human threat. Field research conducted over the past two decades has greatly expanded knowledge of the island's biota, making it difficult for any single research team to maintain up to date estimates of biodiversity and endemism across taxonomic groups. The recent publication of The Natural History of Madagascar, a synthesis by nearly 300 contributors from a wide range of disciplines, provides the means to update these estimates. Here, we summarize biodiversity information presented in the volume by providing revised estimates of species richness, endemism, and state of knowledge of a wide variety of taxonomic groups occurring on the island. Madagascar is a critical priority for international conservation efforts, based on almost unparalleled levels of endemism, species diversity, and human threat. Field research conducted over the past two decades has greatly expanded knowledge of the island's biota, making it difficult for any single research team to maintain up to date estimates of biodiversity and endemism across taxonomic groups. The recent publication of The Natural History of Madagascar, a synthesis by nearly 300 contributors from a wide range of disciplines, provides the means to update these estimates. Here, we summarize biodiversity information presented in the volume by providing revised estimates of species richness, endemism, and state of knowledge of a wide variety of taxonomic groups occurring on the island.