Planthoppers (Hemiptera: Fulgoroidea) comprise a diverse group of more than 12,000 described species of phloem-feeding insects distributed throughout the world. Explanations of diversification of phytophagous insects often involve observed patterns of host plant usage. This hypothesis was tested in a previous study, in which researchers compiled a list of over 1000 planthopper/host plant associations and tested for evolutionary progressions in host plant use across the phylogeny of planthopper families. These researchers employed the most complete phylogeny available at the time, but that phylogeny was based on limited data and failed to provide compelling evidence for relationships among the 20 planthopper families. More recent phylogenetic analyses of planthopper families have suffered from insufficient taxonomic and data sampling, and hypotheses of planthopper phylogeny have remained largely incongruent and incomplete. Here, we present a more complete estimation of planthopper phylogeny, based on analyses of three new nucleotide sequence data sets (18S rDNA, 28S rDNA, and Histone 3) generated from exemplars representing 17 of the 20 planthopper families. We use this phylogeny to retest the hypotheses evaluated in the earlier study: 1) Is there evidence of parallel phylogenesis between planthoppers and their host plants? and 2) Does the phylogeny of planthopper families show a progression in host plant specialization? Because perceived trends in host plant use are likely clearer when addressed at finer taxonomic levels, it is important to investigate relationships within planthopper families, as well. To this end, preliminary results from a phylogenetic analysis of the family Fulgoridae are also presented.