Transmyocardial laser revascularization (TMR) is a relatively new therapy for atherosclerotic coronary artery disease. Unlike well established surgical and percutaneous revascularization procedures, TMR is reserved for patients with advanced and severe forms of coronary artery disease that is unsuitable for other forms of revascularization. The results of TMR so far have been controversial with a bias toward steady and incremental adoption as sole therapy or in combination with coronary artery bypass graft surgery. The controversy surrounding TMR is related to the fact that its mechanism of action is not proven beyond a reasonable doubt. It is believed that angiogensis stimulation by the laser beam may be responsible for the relief of angina. However, the marked discrepancy in the symptomatic relief of angina and the increase in myocardial perfusion is not well understood. Other mechanisms proposed include direct perfusion through the laser channels, myocardial damage, denervation of ischemic myocardium and a placebo effect. It is possible that one or more of these mechanism may be responsible at various time intervals for the relief of angina. The challenge of TMR is related to improvement in perioperative outcomes, and long-term survival without worsening of left ventricular function. The achievement of these goals makes TMR an alternative therapy to what was formerly the only therapeutic option for these patients, namely: failed maximum medical therapy.