Objectives. This study assessed the safety and diagnostic accuracy of adenosine stress myocardial perfusion scintigraphy for the detection of coronary artery disease using single-photon emission computed tomography (SPECT) in patients with significant aortic stenosis. Background. Exercise cardiac stress testing in patients with significant aortic stenosis is generally avoided because of concerns for safety. In addition, those studies that have analyzed the utility of exercise testing both with and without myocardial thallium-201 scintigraphy for the diagnosis of coronary artery disease have yielded low specificity. Currently, no safe and accurate means exists to noninvasively assess the presence, extent and severity of coronary artery disease in patients with significant aortic stenosis. Methods. The study included 35 patients with moderate to severe aortic stenosis (mean [±SD] aortic valve area 0.84 ± 0.16 cm2, range 0.5 to 1.2; mean maximal instantaneous aortic valve gradient 44.4 ± 15.9 mm Hg, range 20 to 84). All patients underwent a 6-min adenosine infusion (140 μg/kg body weight per min) protocol and either separate acquisition rest thallium-201/stress technetium-99m sestamibi or stress and 4-h redistribution thallium-201 SPECT. Visual 20-segment SPECT analysis used a standard five-point scoring system from 0 (normal tracer uptake) to 4 (absent uptake). The SPECT results were considered abnormal if more than two segments had a stress score ≥2. Hemodynamic, electrocardiographic and clinical responses were compared with those in a reference group of 100 consecutive age-matched patients undergoing adenosine SPECT who did not have aortic stenosis. Results. Hemodynamic responses during adenosine stress testing between the study and control patients demonstrated no significant difference in the net change in systolic blood pressure (18% of baseline vs. 14%, patients with aortic stenosis vs. control subjects), heart rate (21% vs. 19%), rate-pressure product (0% vs. 2%) or incidence of chest pain (23% vs. 35%) or transient second- (9% vs. 9%) or third-degree atrioventricular block (3% vs. 1%). In the 20 patients who had coronary angiography, sensitivity for detection of coronary artery disease was 92% (12 of 13) and specificity was 71% (5 of 7). Conclusions. In this preliminary study, adenosine was found to be well tolerated and diagnostically accurate in patients with moderate to severe aortic stenosis.