abstract: baccharis myriocephala is a carqueja species less studied than other baccharis species. this study evaluated the chemical composition, toxicological and antioxidant potentials of the essential oils and infusions of b. myriocephala. essential oils (hydrodistillation) and the volatile fractions of infusions (spe) were analyzed by chromatographic techniques. the tpc and tfc of the infusions, and the antioxidant activities of essential oils and infusions were measured by spectrophotometry; their toxicological potentials were evaluated by artemia salina bioassay (asb). twenty-eight terpenic compounds were identified in the essential oils, fourteen of them for the first time. nine compounds were identified in the volatile fraction of the infusions, and seven of them were absent in essential oils. infusions [ic50(dpph) = 2.21 mg ml-1] are better antioxidants than the essential oils [ic50(dpph) = 40.37 mg ml-1]. the essential oils were considered highly cytotoxic (ld50 = 26.64 g ml-1), according to the asb.