The effect of the industrial treatment with microwaves on the antioxidant activity of herbs and spices was evaluated. Samples of black pepper (Piper nigrum L.), oregano (Origanum vulgare L.), basil (Ocimum basilicum L.) and sage (Salvia officinalis L.) obtained before and after the microwave treatment were extracted with an acetone-water mixture (70:30). the extracts were analyzed for their phenolic content. The antioxidant activity was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) and deoxyribose methods and the prooxidant activity was determined by evaluating the reducing power and the iron chelating capacity. The treatment did not modify the antioxidant properties of these herbs and spices as the majority of the differences between treated and non treated samples were not statistically significant.