AbstractThe activities of isolated compounds and crude extracts from species of the autochthonous flora of the North of Chile, were evaluated againstTrypanosoma cruzitrypomastigotesin vitro.A marked trypanocidal activity was observed for the chloroform, ethanol and methanol‐aqueous extracts ofGelidium pusilum(Gelidiacea). Similar activity was found in the chloroform extract ofMiroglia grandis(Gigartinaceae) and in the methanol + water + chloroform extract ofBacharis boliviensis(Compositae). The most active extracts tested werep‐cumaroiloxitremethone isolated fromParestrephia quadrangularisand two terpenes fromBacharis boliviensis, not yet structurally elucidated (PN‐3 and PN‐59). The screen identifies natural products which are active against blood trypomastigotesin vitroat 4°C and which may be useful in preventing the transmission of Chagas' disease by blood tra