The effects of heat treatment on the radical-scavenging activity of the two phenolic compounds, quercetin and epigallocatechin gallate, were examined. The retained radical-scavenging activity of both polyphenols was 100% and 80% after respective 60-and 480-min heating at 100°C suggesting that common boiling practices do not compromise the antioxidation effects. However, the content of epigallocatechin gallate was significantly decreased, although its radical-scavenging activity remained. With heating at 180°C, both the quercetin and epigallocatechin gallate contents decreased much more rapidly than their radical-scavenging activity, suggesting that the radical-scavenging activity remained in their degradation products. After 15 min of heating at 180°C, the retained radical-scavenging activity of quercetin and epigallocatechin gallate was more than 80%. Therefore, usual high-temperature cooking methods such as deep frying or oven heating would not severely compromise the antioxidation effects of these compounds.