The Beringian Coevolution Project (BCP) is a systematic inventory of the mammals and associated parasites and pathogens of the Beringian region. Primary objectives of the project are to: 1) collect data on mammal and parasite occurrence, distribution, and relative abundance, 2) obtain new collections of mammals and associated parasites which will serve as a basis for comparative morphological, phylogeographic, and phylogenetic studies, 3) archive and loan mammal and parasite frozen tissues for use in molecular analyses of Beringian faunas, 4) continue development of a computerized database that permits assessments of regional diversity and biogeography, and 5) foster international collaborations. The BCP, conducted at the crossroads of the northern continents, will contribute significant insights into historical biogeography, faunal structure, and patterns and processes in speciation of hosts and parasites. It will also serve as a critical model for understanding biodiversity across the Holarctic. This international collaborative effort includes researchers from the Institute of Biological Problems of the North (Magadan, Russia), Vantaa Research Centre (Finland), University of Saskatchewan, Biosystematics and National Parasite Collection (USNPC) Unit of the USDA (Maryland), and Museum of Southwestern Biology (MSB). Collected parasites will be useful for both morphological studies and molecular analyses (frozen or ethanol preserved). Hosts and parasites will be archived at the MSB and USNPC, respectively. This material provides a foundation for comparative phylogeographic studies across Beringia. Studies and collaborations between morphologists and molecular phylogeneticists are encouraged.