Volatile chemicals obtained from a commercial beer by liquid-liquid continuous extraction were evaluated for antioxidant activity. The inhibitory ability of this extract toward the conversion of hexanal to hexanoic acid was monitored over a 35-day period. The volatile extract demonstrated >99% effectiveness at inhibiting hexanal oxidation at 50 microg/mL, comparable to that of the natural antioxidant alpha-tocopherol (vitamin E). Volatile compounds contained in the extract were isolated and identified by gas chromatography-mass spectrometry (GC-MS). From the volatile constituents identified in beer extract, phenylethyl alcohol, maltol, and 2-furanmethanol were examined for antioxidative activities. At a concentration of 500 microg/mL, maltol and 2-furanmethanol demonstrated approximately 95 and 100% inhibition of hexanal oxidation over 35 days, respectively. Phenylethyl alcohol did not show any appreciable level of inhibition of hexanal oxidation. Heterocyclic compounds, some of which are known to possess antioxidative activities, were also identified in the volatile extract.