Studies of the distribution of South American taxa have identified several areas of endemism that may have contributed to the historical diversification of the region. We constructed a phylogeny of Glyphorynchus spirurus (Aves: Dendrocolaptidae) populations using mtDNA sequence data from portions of cytochrome b, NADH dehydrogenase subunit II (ND2), and complete NADH dehydrogenase subunit III (ND3). Using this phylogeny we evaluate five previous hypotheses of area-relationships, two based on phylogenetic studies of morphological characters in birds and three based on parsimony analysis of endemism in birds and primates. Maximum likelihood and maximum parsimony analyses recovered two phylogenetic hypotheses that differed in the placement of one of the areas. Within each of the areas of endemism, the two analyses support the same clades. Neither of the phylogenetic hypotheses for Glyphorynchus exactly matches any of the five previous hypotheses of area-relationships, although ambiguous support exists for one of them. Five areas-Central America, Inambari, Napo, Pará, and Rondônia-are supported as composites with component taxa having phylogenetic affinities with more than one area. Data reported here also indicate high levels of sequence divergence within Glyphorynchus. Genetic breaks within Glyphorynchus are only partially congruent with subspecific taxonomy. The regional sampling design used makes this study the largest scale genetic assay of a widespread Neotropical avian taxon published to date.