This paper assesses the evidence that early, complete and sustained recanalisation of the infarct related artery is the most important factor in limiting myocardial damage and improving outcome after coronary thrombosis. Besides the results of experimental studies, clinical support for the 'open artery' concept comes from, first, the consistent demonstration that patients with patent arteries survive better that those in whom patency is not achieved; second, from the observation that early treatment is associated with a better outcome, and third, from the demonstration that reperfusion by angioplasty or bypass grafting produces results as good or better than those of fibrinolytic therapy. Validation of adequate reperfusion as both the mechanism of, and a surrogate for, improved clinical outcome encourages 'perfusion endpoint' clinical trials to develop new reperfusion strategies.