Cellular metabolism is normally accompanied by generation of small amounts of oxidants. Under certain pathophysiological conditions, the amount of oxidants formed is greatly increased, with consequent oxidative stress, and it is now widely appreciated that this phenomenon may have important consequences. Experimental studies have shown that generation of large amounts of oxygen radicals can occur upon postischemic reflow, inducing a specific form of myocardial damage, that adds on ischemic injury; evidence is accumulating that this phenomenon may also occur in man. Oxidative stress also accompanies experimentally induced heart failure. Its pathogenetic role and possible occurrence in man are hot research topics...