Adenosine myocardial perfusion imaging is useful in diagnosis of coronary artery disease (CAD) and risk assessment in patients who have exercise limitations. As a pharmacologic stressor, adenosine acts on two cell-surface purine receptors, A1 and A2. Activation of A2 receptors cause coronary vasodilation. Unlike other pharmacologic stressors, such as dipyridamole and dobutamine, adenosine is an endogenous biochemical. Adenosine perfusion studies have a relatively high sensitivity and specificity (80%-90%) for identifying CAD. Images from adenosine studies are comparable to, or better than, images from exercise myocardial perfusion studies. The side effects are common, but not serious; they are short-lived and rarely require the administration of aminophylline.