Pseudocyphellaria perpetua McCune & Miadlikowska is described as a new species of lichenized fungus from Oregon, U.S.A. Morphologically similar to some forms of P. crocata, P. perpetua is separated from that species by a yellow medulla and predominantly marginal soralia. Comparison of ITS and LSU nrDNA sequences support taxonomic distinctness of these two species. Phylogenetic analyses were conducted on LSU and ITS nrDNA data sets separately and simultaneously using maximum parsimony and maximum likelihood as optimization criteria. All analyses except one (maximum parsimony on LSU nrDNA data alone) confirmed the monophyly of P. perpetua. There are two distinct groups within the P. perpetua clade represented by specimens sampled from near the type locality in Oregon, and specimens outside of Oregon (eastern Canada, eastern Russia and eastern U.S.A.). The genus Pseudocyphellaria is very likely polyphyletic, consisting of at least two highly divergent groups.