The antioxidant properties oí Acantholippia deserticola, a herb used in traditional northern Chilean medicine was studied using free radical - generating systems. The 50% aqueous - ethanol extract oí Acantholippia deserticola protected against non-enzymatic lipid peroxidation in microsomal membranes of rat, induced by an Fe++ - ascorbate system and measured spectrophotometrically by the TBARS test, and had strong free radical scavenging capacities on stable ABTS and DPPH radicáis. The results shows that the IC50 valué of the 50% aqueous - ethanolic extract oí A.deserticola is 18 ± 0.5 μg/mL in DPPH radical - scavenging, 15 ± 0.8 μg/mL in lipid peroxidation , Total Antioxidant Activity (TAA) is 0.95 mM of Trolox per mg/mL of extract. The total phenolics content of extract is 725 ± 12 mg of gallic acid equivalent per g of dried extract. The results indicate that the 50% aqueous - ethanol extract oí Acantholippia deserticola clearly has antioxidant properties.