Current knowledge about mammalian interordinal relationships is growing rapidly; thus this contribution is an attempt to summarize the past 5 years of this literature. We have focused on the recent controversies in mammalian phylogenetics including hypotheses concerning the monophyly of Archonta, the diphyly of Chiroptera, and the polyphyly of Rodentia. All of these issues have been proposed recently, challenging these phylogenetic hypotheses. We have attempted to include all of the comprehensive analyses of eutherian mammal systematics with an emphasis on morphological and molecular data sets where discrete characters are listed so they could be compiled and used in support of interordinal relationships. Particular attention is given to determining which of the living eutherian orders is the closest relative to primates. In reviewing relationships among the mammals, we have focused on collating all of the available evidence so that one could know where each of the specific data sets is in support of the various relationships.