Myocardial preconditioning describes the profound myocardial protection that follows a short episode of sublethal ischaemia. Adenosine is produced in ischaemic myocardium and is thought to be an important trigger of the protective mechanism. The exact pathway awaits full elucidation but activation of G proteins and subsequently protein kinase C appear to be important signals. End effectors responsible for delaying cell death include opening of K+ATP ion channels and the transcription of a family of cytoprotective proteins. Absolute proof that preconditioning occurs in man is still awaited, although cross clamping of the aorta during cardiac surgery, balloon inflation during coronary angioplasty, warm-up angina and preinfarction angina are surrogate models supporting its existence. A clearer understanding of the protective mechanisms involved could lead to the development of novel therapeutic agents that could save the infarcting myocardium.