Phylogenetic relationships in Mentha were inferred from DNA sequences of the chloroplast (cp) rpl16 intron and trnL-trnF region. The objectives were to test monophyly of Mentha and each of its sections and assess relationships among Mentha species. Based on cpDNA data, Mentha is strongly supported as monophyletic. The suggestions that M. cervina and M. cunninghamii should be placed in other genera gain no support from this analysis. Mentha cervina is sister to M. gattefossei, and the New Zealand endemic, M. cunninghamii, is allied with species from Australia (M. australis, M. diemenica, M. satureioides). No recognized section with more than one species sampled forms a monophyletic group. Section Pulegium may be monophyletic, but the third member of this section, M. grandiflora, was not sampled. Chloroplast DNA sequences of the putative allopolyploids M. canadensis and M. spicata suggest that M. arvensis and M. longifolia, respectively, may be their maternal parents.