Recebido em 8/3/09; aceito em 22/10/09; publicado na web em 9/3/10 VOLATILE LEAF OILS OF Vernonia brasiliana AND Vernonia remotiflora: CHEMICAL COMPOSITION AND BIOLOGICAL ACTIVITY. The chemical composition of the essential oils, obtained by hidrodistillation, from leaves of two Vernonia species (V. remotiflora and V. brasiliana), was determined by GC-FID and GC-MS. Both essential oils were predominantly constituted by sesquiterpenes (92.0 -93.4%). The main constituents of the oil from V. brasilana were (E)-caryophyllene (36.7%), germacrene D (35.5%), and a-humulene (11.7%), while (E)-caryophyllene (42.2%) and bicyclogermacrene (20.0%) were the major ones in the oil from V. remotiflora. Although with moderate activity both oils showed acetylcholinesterase and antibacterial activities.