Biodiversity is a "hot" topic that has recently spawned much interest in the popular and scientific press and in Washington. Part of the reason for this interest has been the fear among scientists and laypersons that we are going to be con- fronted with a mass extinction event driven by human encroachment on the biosphere. The magnitude of the problem, however, is very difficult to assess as it is difficult to deter- mine when and if a particular species, or group of species, is going to go extinct. These considerations provide the back- drop and motivation for Brian Maurer's book Geographical population analysis, which is one of a series of books edited by John Lawton and Gene Likens for Blackwell Scientific Publications entitled Methods in Ecology. The books in this series are intended to provide an overview of new and emerging techniques that can be applied to ecological problems. In the case of Geographical population analysis, this entails analytical techniques for assessing the status of a species by analyzing patterns of distribution and abundance over its en- tire geographic range.