The purpose of this study was to evaluate the striatal dopamine D-2 receptor density in infants with perinatal hypoxic-ischemic brain injury (HIBI) using I-123-iodobenzamide (IBZM) brain SPECT and to correlate the findings with the severity of HIBI and neurologic outcome. Methods: Twenty infants who were diagnosed to have perinatal HIBI were included in this study. They were classified as having mild (n = 6), moderate (n = 10) or severe (n = 4) HIBI according to their neurologic findings at birth using the criteria of Sarnat and Sarnat, Neurologic outcome of these infants was determined by serial neurologic examinations and the Denver developmental screening test; 10 infants recovered without any deficit and the remaining 10 were affected to a degree varying from motor impairment to cerebral palsy. All 20 infants were examined using I-123-IBZM brain SPECT at age 7.8 +/- 2.3 mo. Transaxial slices were obtained 2 hr after intravenous injection of 300 mu ci (11.1 MBq) I-123-IBZM and the activity ratios of striatal to occipital cortex (ST/OC) were calculated. Results: The mean ST/OC ratios in patients with mild, moderate and severe HIBI (1.219 +/- 0.078, 1.097 +/- 0.069 and 0.813 +/- 0.140, respectively) were significantly different from each other (p = 0.001). The infants who recovered from HIBI without any neurologic sequelae had higher mean ST/OC ratios than the others (1.184 +/- 0.010 versus 0.969 +/- 0.160, p = 0.002). Conclusion: The results of this study show that in infants with HIBI, striatal D-2 receptor density decreases as the severity of injury increases. The D-2 receptor density is higher in infants who recover without neurologic deficits compared to those who are affected neurologically. Dopamine D-2 receptor imaging can be used to assess the severity of HIBI in children.