The family Kermesidae in North America is revised for the first time, based on slide-mounted, newly-molted young adult females. Fifteen species are redescribed, four are synonymized, and four are described as new. A literature review is given for these and 14 other species for which slide-mounted specimens were not available. Two new genera, Allokermes and Nanokermes, are proposed and described, and with the genera Kermes and 01/iffiella a re placed in the family Kermesidae. The third instar of one species in each genus is described and illustrated. Keys are given to the genera, based on both third instar females and newly-molted adult females, and to the species in each genus. Known host plants and geographical distribution records are listed for each species. The brood chamber of Allokermes rattani Ehrhorn is described and illustrated, and the mechanism for the escape of the first instars from the brood chamber is illustrated. Using Hennig's (1965) method, the phylogenetic inter-relationships among the genera are determined.