The risk stratification of conservatively managed patients presenting with non-ST elevation (NSTE) acute coronary syndromes (ACS) is frequently accomplished by the use of myocardial perfusion scintigraphy (MPS) in clinical practice. However, whether one can predict the extent of coronary artery disease (CAD) on angiography by MPS in this setting is unknown. In this study, the correspondence of findings on MPS to those on coronary angiography was retrospectively analyzed in 55 patients presenting with NSTE ACS. Patients' mean age was 64 years, 55% were men, and 87% had positive troponins. Of these patients, 42% of patients with perfusion defects involving the anterior wall presented with significant extensive CAD on coronary angiography, consisting of left main disease, 3-vessel disease, or 2-vessel disease involving the left anterior descending coronary artery. In patients with perfusion defects limited to 1 territory, 50% also had extensive CAD. A "negative" result on MPS was associated with extensive CAD in 37% of patients and the absence of significant lesions in only 8%. In conclusion, these findings suggest that MPS alone may be of limited clinical utility in distinguishing troponin-positive NSTE ACS patients with extensive CAD from those with more limited disease and should prompt further investigation of the use of MPS for this indication.