The antioxidative activities of hamamelitannin (2′, 5-di-O-galloyl-hamamelose), gallic acid anddl-α-tocopherol against lipid peroxyl radicals were evaluated in chemical and biological systems. The peroxyl radical scavenging activity was evaluated by electron spin resonance (ESR) method in which both spin-trapping and direct reaction methods were used. In the spin-trapping method, as evaluated by 50%inhibition concentration (IC50) of peroxyl radicals generated in a t-butylhydroperoxide-methemoglobin system, hamamelitannin (IC50= 95.3±2.7μM) showed the highest activity, followed by gallic acid (IC50= 152.8±14.6μM) anddl-α-tocopherol (IC50= 221.5±4.6μM) as a positive control. When estimating by the direct method, IC50values of hamamelitannin, gallic acid anddl-α-tocopherol were 93.5±2.1μM, 141.6±2.0μM and 1590.0±330.0μM, respectively.On peroxidation of lipid bilayers induced by 2, 2′-azobis-(2-amidinopropane)dihydrochloride(AAPH) in terms of inhibition period (tinh), hamamelitannin showed the longest tinh time (1107.0±38.18 sec), followed by those ofdl-α-tocopherol (877.5±31.8 sec) and gallic acid (771.0±4.2 sec). The kinetic chain length, defined as the propagation numbers of a lipid peroxyl radical, and calculated from the ratio (Rp/Ri) of the rate of lipid peroxidation to that of inhibition bydl-α-tocopherol, hamamelitannin and gallic acid were 27.23, 7.86 and 7.09, respectively. The effects of hamamelitannin, gallic acid anddl-α-tocopherol were evaluated on murine fibroblasts exposed to t-butylhydroperoxide (BHP) in terms of the cell survivals. In the protection, hamamelitannin induced the highest survival of 27.6±0.6 % at 50μM, while both gallic acid and dl-α-tocopherol were less active at the same concentrations. On the basis of the results, hamamelitannin was concluded to have a high protective activity on cell damage induced by peroxides.