The effects of seven phenolic compounds isolated from Salvia miltiorrhiza on peroxidative damage to liver microsomes, hepatocytes and erythrocytes of rats were studied. The results show that the seven compounds inhibited lipid peroxidation of rat liver microsomes induced by iron/cysteine and Vitamin C/NADPH. The hemolysis of rat erythrocytes induced by hydrogen peroxide was also inhibited. The degree of inhibition varied with different compounds. Among the seven compounds, the action of salvianolic acid A (Sai A) was the most potent. Therefore, the protective action of Sai A against peroxidative damage to isolated rat hepatocytes and their plasma membranes was evaluated further. Malondialdehyde (MDA) production and bleb of the surfaces of rat hepatocytes induced by iron/cysteine were prevented by Sai A. The production of MDA and the consumption of NADPH of the plasma membrane during lipid peroxidation initiated by iron/cysteine and Vitamin C/NADPH were also inhibited. The results strongly suggest that several phenolic compounds like Sai A have a protective action against peroxidative damage to biomembranes.