the species of piper are of great medical interest. they, however, represent considerable taxonomic challenge, probably due to the small size of floral parts. therefore, the external morphology of the leaf has been used as diagnostic features in the taxonomy of the group. however, there are few anatomical studies on species of this genus. in this study, the leaves of nine species were compared anatomically: piper aduncum vell., p. cernuum vell., p. dilatatum rich, p. gaudichaudianum kunth, p. glabratum kunth, p. hispidinervum c. dc., p. lindbergii c. dc., p. solmsianum c. dc. and p. umbellatum jacq. the objective was to evaluate the potential of anatomical characters for species separation. most species studied have the epidermis of the lamina consists of rectangular and rounded cells. subepidermal layers occur on both sides of the lamina, except in p. aduncum, p. cernuum and p. hispidinervum. all species are hypostomatic, except p. hispidinervum. the mesophyll is dorsiventral in most species, while in p. solmsianum and p. umbellatum, the mesophyll is homogeneous. the number of layers of palisade and spongy tissue is variable. also there are variations in the number and size of vascular bundles. in general, secreting cells, idioblasts, and glandular trichomes, lipids, phenolic compounds and starch are present. cluster analysis identified three distinct groups of species based on anatomical features studied.