We present two patients who exhibited striking abnormalities on stress thallium-201 scintigrams, suggesting ventricular aneurysm before documentation of this diagnosis by contrast ventriculography. The features of the scintigrams included: (a) a large perfusion defect overlying the cavity of the left ventricle, the defect extending to the periphery of the cardiac image and containing fewer counts than the lung background; (b) relatively increased lung background; (c) increased right-ventricular prominence; and (d) abnormal cardiac contour. Although large aneurysms of the left ventricle can usually be diagnosed from history and physical examination, occasionally they can be more subtle in their manifestations. Appearance of a myocardial perfusion image as described above should alert the physician to the possibility of this diagnosis.