SOD (Superoxide dismutase)-like activities of 23 kinds of single malt whisky (Scotch and Japanese) were evaluated. There was a positive correlation between SOD-like activity and the maturation age of whisky that exceeded the difference resulting from the manufacturing region. The SOD-like activity of Yamazaki 18, a typical single malt whisky in Japan, was approximately 1333 U/ml and that of non-volatile components in the whisky was 388 U/mg, indicating that single malt whisky generally has a very strong SOD-like activity. To elucidate their contribution to SOD-like activity, the non-volatile components of whisky (Yamazaki 18) were ultrafiltered and separated with a Diaion HP20/water-EtOH system. Elution of the fraction less than 5000 molecular weight (<5000 MW fraction) with 60% (v/v) EtOH contributed most to SOD-like activity of the whisky. As this elution contained a considerable amount of polyphenolics, the content and SOD-like specific activity of ellagic acid, gallic acid, and lyoniresinol - the main whisky polyphenolics - were evaluated. The contribution of these compounds to the SOD-like activity of whisky was approximately 15%. Polyphenolics in whisky were relatively distributed to a higher MW fraction compared to carbohydrates in whisky, and specific activity (SOD-like activity per weight) of the >10,000 MW fraction was greater than that of the <5000 MW fraction, although the content of this fraction was low. These results indicate that various polyphenolics with higher molecular weights also contribute to the SOD-like activity of whisky together with main whisky polyphenolics. (C) 2011, The Society for Biotechnology, Japan. All rights reserved.