The single-copy DNA sequences of the Bank Swallow (R. riparia) and the Barn Swallow (Hirundo rustica) were radio-labeled and compared with the DNAs of an array of other oscine species, using the technique of DNA-DNA hybridization. The results indicate that the swallows shared a most recent common ancestor with the sylviine-timaliine cluster, and that the divergence probably occurred ca. 50 mya, in the Eocene. The white-eyes (Zosterops) are also related to the swallow-warbler-babbler complex, as are the titmice, kinglets, bulbuls, nuthatches, creepers, wrens, verdins, and gnatcatchers. The fringillid-ploceid assemblage is the sister group of the swallow-warbler-babbler assemblage, with the muscicapine-turdine, and the corvine assemblages being progressively more distant.