The beneficial effect of naturally occurring flavonoids in health is believed to be due to their strong antioxidant activity. However, recent laboratory evidence indicates the involvement of a more specific action. Here, we present evidence that, among a number of catechins present in green tea extract, only epigallocatechin-3-gallate (EGCG) exerts a strong inhibitory action on interferon-gamma-elicited activation of signal transducer and activator of transcription 1 (STAT1). Protective action of EGCG in ischemia/reperfusion injury in the heart and the molecular mechanism of action, which has nothing to do with its anti-oxidant capacity are described.