Attenuated end-diastolic and end-systolic left ventricular counts which obtained from cardiac gated blood pool scan were corrected using experimentally calculated attenuation coefficient $(mu=0.13/cm)$ and depth of center of left ventricle. This method was confirmed to be correct experimentally using phantom balloon. To compare the accuracy of attenuated and attenuation-corrected left ventricular volume measurement, authors studied 10 patients with ischemic heart disease who underwent both gated blood pool scan and X-ray contrast ventriculography within a week. The attenuated and attenuation-corrected left ventricular volume measured by count method correlated with contrast ventriculographic volumes; however, attenuation corrected measurement was correlated more closely.