Institute of Molecular Cardiology, University of Louisville, Louisville, Kentucky The discovery of preconditioning (PC) has arguably been the single most important development in the field of ischemic biology in the past 20 years. The significance of this phenomenon transcends cardiovascular medicine, since it is ubiquitously observed in virtually every tissue of the body. This article reviews the pathophysiology and molecular basis of myocardial PC, with particular emphasis on the late phase of this cardioprotective adaptation. The article also discusses the exploitation of late PC for the development of novel gene therapy strategies aimed at inducing a permanently preconditioned cardiac phenotype (prophylactic cardioprotection). Besides its conceptual interest, deciphering the mechanism of late PC has considerable therapeutic reverberations, since transfer of the genes that underlie late PC would be expected to emulate the salubrious effects of this response of the heart to stress. nitric oxide synthase; protection; cyclooxygenase-2 Address for reprint requests and other correspondence: R. Bolli, Division of Cardiology, Univ. of Louisville, 550 S. Jackson St., ACB, 3rd floor, Louisville, KY 40292 (E-mail: rbolli{at}louisville.edu )