To standardize the regional cerebral count with 99mTc-HMPAO, equilibrium blood count of which trapping mechanism is the same as the brain was used in seven patients with cerebrovascular disease. We injected 99mTc-HMPAO 740 MBq in 10-15 sec and got sequential arterial sampling in patients who were undertaken with PET. Four hours later 99mTc-HMPAO brain SPECT was taken and a venous sampling was drawn for determining the equilibrium blood count. Correlation between the area of arterial time activity curve and equilibrium venous blood count was 0.93. After 44 regions (36 in cortical area, 8 in deep area) with 99mTc-HMPAO brain SPECT were placed, SPECT counts were corrected by standardization of equilibrium venous blood count. The correlation between rCBF determined from C15O2 PET and corrected SPECT counts was 0.80 and 0.67, cortical area and deep area, respectively. We concluded that 99mTc-HMPAO brain SPECT count can be corrected by equilibrium blood count to standardize the regional cerebral counts.