SPECIES conservation in situ requires networks of protected areas selected for high conservation interest. Throughout most of the world, however, there are neither the resources nor the time to carry out detailed inventories for most taxa, before designating protected areas. Site selection (on grounds other than availability) would be easier and more effective if two things were true: (1) habitats that are species-rich for one taxon are also species-rich for others; and (2) rare species occur in, and therefore benefit from the conservation of, species-rich habitats. Diversity (usually, species richness) and the presence of rare species are the most frequently cited criteria for site selection by conservationists. Here, we use data on British plants and animals held by the Biological Records Centre (BRC) and the British Trust for Ornithology (BTO), mapped on a grid of 10 km x 10 km ('10 km squares') to examine the extent to which species-rich areas for different taxa coincide, and whether species-rich areas contain substantial numbers of rare species. The fine scale and high intensity of recording in Britain produces distributional datasets at least as good as and, in most cases, better than those available elsewhere. For Britain at least, we do not find strong support for either proposition. Species-rich areas ('hotspots') frequently do not coincide for different taxa, and many rare species do not occur in the most species-rich squares.