The methanolic and methane dichloride extracts of aerial parts of Larrea divaricata Cay. (Jarilla) plants exhibited a pronounced cytotoxic effect by arresting cell viability at a level of 35% against the MCF-7 cell line, a human breast adenocarcinoma, while only a weak cytotoxic effect was observed for the aqueous extract. Apoptosis was detected by flow cytometry, using annexin V and by cytological detection with fluorescein diacetate / propidium iodide staining. The annexin V, as well as the uptake of fluorescein diacetate/propidium iodide staining, revealed that methanolic and methane dichloride extracts of L. divaricata treatment of cells resulted in a rapid plasma membrane perturbation and triggered cellular death (>70%). Methanolic extracts were submitted to further treatment by bioassay-guided purification, involving fractionation and chromatography. 0.1% (w/w) nordihydroguaiaretic acid (NDGA) was found, which displayed weak citotoxic activity.