The Nahua of the Mexican state of Veracruz use Baccharis conferta in the treatment of a variety of gastrointestinal illnesses, especially diarrhoea associated with gastrointestinal cramps. The aerial parts of B. conferta were investigated phytochemically and pharmacologically using the guinea pig ileum assay as a model (histamine, KCI and electric stimulation). The crude ethanolic extract showed a dose-dependent antispasmodic effect that was particularly strong in flavonoid-rich fractions (e.g. IC50 value for fraction E.3.1 from the ethyl acetate fraction, in histamine-induced contraction, 10 microg mL(-1)). Several flavonoids (apigenin-4',7-dimethylether, naringenin-4',7-dimethylether, pectolinarigenin and cirsimaritin) were isolated, while others were identified in complex fractions by GC-MS. The flavonoids play an important role in the antispasmodic activity of this indigenous drug. Additionally, oleanolic acid and its methyl ester as well as erythrodiol were isolated. Oleanolic acid methyl ester shows weak antibacterial activity against M. luteusand E. coli (20 microg/spot in a TLC assay). The phytochemical as well as the pharmacological data provide some in-vitro evidence forthe use of B. conferta in thetreatment of gastrointestinal cramps.