The in vitro oxidative hemolysis of human red blood cells (RBCs) was used as a model to study the free radical-induced damage of biological membranes and the protective effect of resveratrol (3,5,4′-trihydroxy-trans-stilbene, 1) and its analogues, i.e., 4-hydroxy-trans-stilbene (2), 3,5-dihydroxy-trans-stilbene (3), 3,4-dihydroxy-trans-stilbene (4), 4,4′-dihydroxy-trans-stilbene (5) and 2,4,4′-trihydroxy-trans-stilbene (6). The hemolysis of RBCs was induced by a water-soluble free radical initiator 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH). It was found that addition of AAPH at 37 ℃ to the suspension of RBCs caused fast hemolysis after a short period of inhibition period, and addition of 1-6 significantly suppressed the hemolysis. Compound 4 which bears an ortho-dihydroxyl functionality showed much more effective anti-hemolysis activity than that of resveratrol and the other analogues. The in vitro oxidative hemolysis of human red blood cells (RBCs) was used as a model to study the free radical-induced damage of biological membranes and the protective effect of resveratrol (3,5,4’-trihydroxy-trans-stilbene, 1 ) and its analogues, ie 4-hydroxy-trans-stilbene (2), 3,5-dihydroxy-trans-stilbene -hens-stilbene (5) and 2,4,4’-trihydroxy-trans-stilbene (6). The hemolysis of RBCs was induced by a water- soluble free radical initiator 2,2’-azobis (2-amidinopropane hydrochloride) (AAPH). It was found that addition of AAPH at 37 ° C to the suspension of RBCs caused fast hemolysis after a short period of inhibition period, and additions of 1-6 significantly suppressed the hemolysis. Compound 4 which bears an ortho-dihydroxyl functionality showed much more effective anti-hemolysis activity than that of resveratrol and the other analogues.