Although classic ischemic preconditioning has been shown to produce a marked reduction in myocardial infarct size in all species tested, its clinical potential is limited by its relatively shortlived duration (30 to 120 min). However, recent evidence has demonstrated that a delayed protective effect reappears 12 to 24 h following acute preconditioning, and this has been termed the second window of protection. Delayed preconditioning differs from classic preconditioning in that it has been shown to produce a cardioprotective effect against both infarction and myocardial stunning. The mechanisms responsible for the cardioprotective effect of classic and delayed preconditioning in reducing infarct size have many similarities, buth those responsible for delayed preconditioning against stunning may be different. Several pharmacological agents have been shown to produce delayed preconditioning, which suggests that it may be exploited clinically...