The world fauna of the order Siphonaptera is reviewed with respect to undescribed taxa, endangered species, taxonomic specialists, developmental stages, ultrastructure, taxonomic characters, host specificity, literature, fossil record, and the phylogenetic affinities of and within the order. The 15 currently recognized families are discussed with respect to their subfamilial, tribal, and generic classification. The numbers of species in these taxa are discussed and their general distribution and host preferences are briefly outlined. The current numbers of tribes, genera, and species, including invalid names, are listed.