The fossil record of mammals records a major interchange of northern and southern faunas in the New World, upon closure of the Panamanian isthmus approximately 3 Mya, termed the Great American Biotic Interchange (GABI). Due to their poor preservation in the fossil record, the degree of participation of birds in this interchange remains largely unknown. A phylogeny for wrens of the genus Campylorhynchus (Aves: Passeriformes) was reconstructed using DNA sequences from the mitochondrial control region and cytochrome b gene. This phylogeny, in combination with biogeographical inference and molecular clock methods, allows estimates of the importance of Late Pliocene interchange to the history of the group. Biogeographical reconstructions and divergence date estimates suggest that the genus began diversification in North America prior to closure of the Panamanian isthmus, consistent with a hypothesized North American origin for the family Troglodytidae. These reconstructions are consistent with pre-GABI dispersal of at most a single Campylorhynchus lineage into South America, with subsequent dispersal of additional lineages, probably across the fully formed isthmus. Increased sampling of avian taxa with widespread New World distributions will continue to clarify the timing and direction of continental interchange. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 687–702.