Adenosine and dipyridamole, the currently available vasodilators for myocardial perfusion imaging, produce hyperemic coronary flow by stimulating A(2A) adenosine receptors on arteriolar vascular smooth muscle cells. However, both vasodilators nonselectively activate A(1), A(2B), and A(3) adenosine receptors, which contributes to common undesirable effects. In the development of a novel pharmacologic stress agent, more selective agonism of the A(2A) receptor subtype would be desirable. Currently, 2 selective A(2A) adenosine receptor agonists are being evaluated in phase 3 studies as pharmacologic stress agents. The highly selective, potent, low-affinity A(2A) adenosine agonist regadenoson (also known as CVT-3146) holds significant potential as a pharmacologic stress agent, based on available results from experimental and clinical trials. Regadenoson produces maximal hyperemia quickly and maintains it for an optimal duration that is practical for radionuclide myocardial perfusion imaging. Regadenoson's simple rapid bolus administration and short duration of hyperemic effect point to an advantage of enhanced control for the clinician.