Mikania glomerata Sprengel and Mikania laevigata Schultz Bip. ex Baker are native Brazilian lianas popularly known as guaco and mainly used as bronchodilators. Based on morphological and anatomical leaf features preliminary data indicate substantial similarity between the two species requiring further studies to increase the accuracy of their diagnosis. However it is still unclear which of the two species is commercially sold. Therefore in the anatomical analysis three individuals of each species were treated according to the usual methodology for stem anatomy. Molecular analysis was performed on four specimens of M. glomerata and six of M. laevigata using three plastid loci (matK rbcL and trnH-psbA) and the ITS2 locus which have been proposed as plant barcodes. Our results including anatomical descriptions and statistically derived quantitative data show that the anatomical structural standard is very similar between the species. Molecular data corroborate the morphological data in pointing to the total similarity between the two species observed in the loci used. Based on these results we conclude that M. laevigata and M. glomerata could be unified in terms of nomenclature.