The technique of DNA-DNA hybridization was used to compare the nuclear DNAs of the Brown Treecreeper Climacteris picumnus and the Rufous Treecreeper Climacteris rufa with the DNAs of other passerine taxa. The treecreepers were found to be the descendants of the oldest dichotomy (ca. 45-48 MYA) in the superfamily Menuroidea, a group that also includes the lyrebirds, scrub-birds, and bowerbirds. We recognize the family Climacteridae, superfamily Menuroidea, parvorder Corvi, suborder Passeres. Within the Climacteridae we recognize two genera, Climacteris for the species picumnus, rufa, melanura, erythrops, and affinis, and Cormobates for leucophaea (including minor) and placens.