Background and aim: Larrea divaricata Cav. (Zygophyllaceae) is a plant widely used in Argentina. Material and methods: We isolated different fractions of L. divaricata aqueous extract containing minor amounts of NDGA, and we analyzed these fractions on mouse macrophages. Results: We showed that a fraction without NDGA was capableof activating macrophages, principally through the production of mitochondrial anion superoxide and H2O2. This could be important in the defense of infections. Moreover, this fraction decreased NO level suggesting an anti-inflammatory action. Conclusion: These results indicate that NDGA was not the compound responsible for the immunomodulatory action exerted by the aqueous extract from L. divaricata. [ABSTRACT FROM AUTHOR]