Xenon-133 inhalation hemispheric cerebral blood flow (HCBF) determinations at one to two days and four to six days postnatally and at 37 weeks postconceptual age have been correlated with computed tomography (CT) scan and autopsy findings in 15 preterm infants weighing less than 1,250 gm at birth. Ten of these infants had germinal matrix hemorrhages (GMH) or intraventricular hemorrhages (IVH). Although HCBF obtained at one to two days showed no mean difference between the GMH/IVH group and the nonhemorrhage infants, hemispheric flow ratios showed significant discrepancies in the GMH/IVH group. In addition, in four of five patients in whom the hemorrhage appeared asymmetric on CT scan, the side of higher flow correlated with the hemorrhage. At four to six days HCBF showed a lower mean value in the GMH/IVH patients than in the nonhemorrhage patients and differences in the interhemispheric ratios in the GMH/IVH group persisted. There were no differences in the mean HCBF values or hemispheric ratios between the two groups of infants at 37 weeks postconceptual age.