The extraction of Tb(III), Dy(III), Ho(III), Er(III), Tm(III), and Yb(III) with 5,7-dibromo-8-hydroxyquinoline (Hdbq or HA) in chloroform from aqueous perchlorate solutions was investigated. The formation of the LnA 3 species (where Ln ¼ Tb, Dy, Ho, Er, Tm, and Yb) in the organic phase was supported by the data. The parameters of the extraction processes were determined, and the separation factors between two adjacent lanthanides(III) were calculated.