Abstract The relationships between the six known species of Rehmannia were investigated. With regard to the content of iridoid glucosides, caffeoyl phenylethanoid glycosides (CPGs) and ionone glucosides, no conclusions could be drawn. Phylogenetic analysis of DNA sequence data (ITS region, trnL-F region and rps 16 intron) reveal a well-resolved topology in which Rehmannia glutinosa and Rehmannia solanifolia and Rehmannia piasezkii and Rehmannia elata are well-supported species pairs. Rehmannia chingii is sister to the rest of the genus, which is congruent with its distribution distant to the other species of the genus.