Deltocephalinae is currently the most diverse subfamily of leafhoppers, containing over 6500 described species placed in nearly 800 genera. Recent phylogenetic analyses of Cicadellidae based on morphology and molecular data and more detailed analyses of Deltocephalinae and related subfamilies based on morphology have shown that Deltocephalinae is polyphyletic. At least eight subfamilies which are recognized in the most recent comprehensive classification of leafhoppers appear to be derived from within Deltocephalinae. However, these previous analyses either had very limited taxon sampling or resulted in low branch support. Thus, the current understanding of relationships in this group is incomplete. The purpose of this analysis is to expand taxon sampling and to add molecular data to an existing morphological data set to obtain a more robust phylogeny that can be used to readdress the higher classification of the group and to infer evolutionary patterns of host plant use. 119 morphological characters and ~2700 bp of the nuclear 28S rDNA gene region were assembled and analyzed for 100 taxa. Combined parsimony and Bayesian analyses yielded trees that are generally consistent in topology with previous phylogenetic estimates of the group. The molecular data contributed support for many nodes on the tree and suggested some relationships that were not supported by morphology alone. Specialization on grasses and sedges occurs ubiquitously in at least 12 tribes treated here, and is shown to be a relatively conserved trait.