The anti-oxidative effects of R8605, a compound of the third generation retinoids, have been studied. R8605 exhibited pronounced inhibitory effects on FeSO4/cysteine and NADPH/vitamin C-induced lipid peroxidation of rat liver microsome as well as on H2O2-induced lipid peroxidation of erythrocytes: Their IC50's were 9.8, 17.6 and 20.3 mumol/L, respectively. R8605 decreased the generation of superoxide anion (O2-.) in a xanthine/xanthine oxidase system and also elevated hepatic superoxide dismutase (SOD) activity in mice. Therefore R8605 shows potent antioxidative effects and this is likely of importance in its chemopreventive actions.