The antioxidant effects of aqueous methanolic extracts from three medicinal Lamiaceae species were investigated in enzyme-dependent and enzyme-independent lipid peroxidation systems. All these extracts caused a considerable concentration-dependent inhibition of lipid peroxidation. Phenolic components present in the plant extracts were evaluated for antioxidant activity and were found effective in both tests. Their concentrations in each extract were determined by TLC-densitometry.