|Abstract||We revisit acanthuroid relationships based on an increasing body of evidence that tetraodontiforms, lophiiforms, and caproids share a close relationship with the acanthuroid fishes. Phylogenetic relationships among the acanthuroids, tetraodontiforms, lophiiforms, and caproids were reconstructed based on data from portions of five nuclear genes (RAG1, zic1, myh6, plagl2, and ENC1). The data were partitioned according to gene and codon position and analyzed using Bayesian, maximum parsimony, and maximum likelihood criteria. All methods of analysis corroborated a restricted Acanthuroidei comprising Acanthuridae, Zanclidae, and Luvaridae. They failed to corroborate the inclusion of Siganidae, Scatophagidae and Ephippidae. The primary reason for this is that two groups previously hypothesized to be basal within Acanthuroidei (scatophagids and siganids) grouped within a clade comprising Antigonia, Lophiiformes, and Tetraodontiformes, while the other presumed basal relatives (Drepane + Ephippidae) were recovered within a larger clade that also includes Monodactylidae, Emmelichthyidae, Sparoidea, Haemulidae, and Pomacanthidae. While the molecular data presented here appear to contradict the results of previous morphology-based studies, we suggest that such a conclusion is unjustified without first surveying putative morphological synapomorphies for the acanthuroids in a broader range of taxa.