Phenolics, common plant constituents form up an important part of human diet and are considered potential chemopreventive agents. In the present study three structurally diverse phenolic acids: protocatechuic, chlorogenic and tannic acid were investigated for their ability to inhibit lipid peroxidation and induce of antioxidant enzymes in mouse epidermis and in rat liver and kidney. All three phenolics significantly decreased the level of lipid peroxidation in the epidermal, hepatic and renal microsomes in vitro. The non enzymatic lipid peroxidation was more affected. The most potent inhibitor of lipid peroxidation in all systems was tannic acid (IC₅₀ = 2.5-13.0 µM). In addition, all tested compounds significantly enhanced the activities of cytosolic glutathione peroxidase (GPx), especially GPx II. Again, the most effective inducer of this enzyme was tannic acid, which increased the level of enzyme activity by 100-300%. Our results indicate that the phenolic acids, ubiquitous food components, particularly those with higher degree of ring hydroxylation, may inhibit or modulate the oxidative damage in the cell.