Using the techniques of direct optimization and sensitivity analysis, the phylogenetics of polychrotid lizards were examined on the basis of both molecular and morphological data (ca. 1040 bp of 12S rDNA, valine tDNA, and 16S rDNA, and 82 characters of morphology). A sensitivity analysis of sequence alignment and morphological change cost functions demonstrated that equal weighting provided the most parsimonious solution for all data. The Polychrotidae is found not to be monophyletic, containing instead the Corytophanidae as the sister taxon of Anolis plus Polychrus Based on these and other results over the last 12 years, the taxonomy of the Iguania is reformulated, with the Iguania composed of two subsidiary taxa, Acrodonta and Pleurodonta, the Acrodonta containing the likely paraphyletic and basally unresolved “Agamidae” as well as the Chamaeleonidae, and the Pleurodonta containing the Corytophanidae, Crotaphytidae, Hoplocercidae, Iguanidae, Leiocephalidae (newly elevated from its former status as a subfamily of the Tropiduridae), Leiosauridae (new taxon including Anisolepis, Aperopristis, Diplolaemus, Enyalius, Leiosaurus, Pristidactylus and Urostrophus), Liolaemidae (newly elevated from its former status as a subfamily of the Tropiduridae), Opluridae, Phrynosomatidae, Polychrotidae (restricted to Anolis and Polychrus), and Tropiduridae (excluding the former subfamilies Leiocephalinae and Liolaeminae).