The phylogenetic associations of North American scorpion genera are examined. Several taxonomic changes are supported by new hypotheses of relationship. The subfamily Syntropinae is synonymized under Vaejovinae. Chactidae and Vaejovidae are restricted to their nominate subfamilies. Superstitioninae, Euscorpiinae, and Scorpiopsinae are raised to family rank. The subfamily Megacorminae is synonymized under Euscorpiinae. Anuroctonus Thorell and Nullibrotheas Williams are removed from Vaejovidae and placed in Iuridae and Chactidae, respectively. Troglotayosicus Lourenco and Belisarius Simon are transferred from Chactidae to Superstitionidae. Twelve species are transferred from Vaejovis Koch to Pseudouroctonus Stahnke. The diplocentrid genus Bioculus Stahnke is resurrected to contain four species from Baja California Sur, Mexico, that were traditionally placed in Didymocentrus Kraepelin. Paruroctonus (Smeringurus) Haradon is raised to the rank of genus. An illustrated key and annotated checklist are provided for the identification of the seven families and 25 genera of North American scorpions.