A better understanding of biodiversity and its current threats is urgently needed, especially in the Netherlands where high population density, industrialisation, and intensive land-use have radically altered the natural landscape. Often, biodiversity research is seriously hampered by a lack of data. This is not so much a problem in the Netherlands, one of the most intensively inventoried countries of the world. Over the last decades, data on the occurrence of a broad range of species have become digitally available in the form of large geo-referenced databases that can be used for spatial analyses. Data from several of such databases were used in this research, which aims at gaining insight in the spatial organisation of Dutch biodiversity, using a broad array of taxonomic groups: hoverflies (Syrphidae), dragonflies (Odonata), mosses (Bryophyta), grasshoppers and crickets (Orthoptera), and herpetofauna (Reptilia and Amphibia). The objectives of this study are threefold: to assess the potential of Dutch species occurrence databases for biodiversity studies; to describe spatial patterns of species richness and composition for different taxonomic groups and relate them to environmental factors; and to analyse the implications of the results for nature conservation. Patterns of species richness of the different groups showed a fairly positive correlation. In broad outline, in the southeastern part of the country more species are found than in the northwestern part, with the dune area as an important exception. A multiple regression analysis revealed which environmental factors may play a role in the mechanisms underlying these patterns. Heterogeneity of the landscape (e.g. number of habitat types, altitudinal range) explained most of the variation in species richness. Biodiversity is not just about species numbers; an area may be relatively poor in species but can still be of high value when the species occurring there do not occur anywhere else. Based on the distribution of the species from the five studied taxa, ...