Previously published morphological and behavioral data for the tyrant flycatchers (Tyrannidae) were reanalyzed using cladistic techniques. Several additional characters, including two putative synapomorphies of the Tyrannidae were incorporated. Nearly all of the ∼100 traditional tyrannid genera were included. Results of the analysis of this set of 68 characters support three previously proposed tyrannid assemblages: the kingbird assemblage and slightly restricted Empidonax and Myiarchus assemblages. Characters of the nasal septum that past workers have considered conservative and phylogenetically informative are supported as synapomorphies of the kingbird and restricted Empidonax assemblages. Several small monophyletic groups of genera are supported. The monophyly of neither the Elaenia assemblage nor the flatbill and tody-tyrant assemblage is supported in any most-parsimonious tree, but such trees are not significantly better than trees supporting their monophyly. A Tyrannidae exclusive of the Cotingidae and Pipridae is monophyletic in some most-parsimonious trees, but not in others in which flatbills and tody-tyrants are basal to a clade containing Cotingidae, Pipridae, and the remaining tyrannid genera. There is some evidence that characters describing plumage color pattern are more homoplasious than the other character suites I examined.