Cerebral blood flow (CBF) and local cerebral glucose utilization (LCGU) were measured using radioactive microspheres and [14C]2-deoxyglucose, respectively, in 26 brain regions in control animals(n = 8)and in animals (n=4) sustaining low-level experimental brain injury. Examination of the initial (resting) CBF measurement in the uninjured cats revealed two subgroups with significantly (p<0-01) different CBF levels. In uninjured cats with normal CBF levels (33-4±1-8 ml/100 g/min) there was a close linear relationship between CBF and LCGU (n = 0-71, P<0-01). In contrast, the remainder of the uninjured cats exhibited abnormally high levels of CBF (72-6±9-9 ml/100 g/min) and the absence of a close relationship between CBF and LCGU (r= 0-27). One hour following low-level (20 atm) fluid percussion brain injury, CBF was increased and LCGU was decreased, though not significantly. The relationship between CBF and LCGU remained intact (r= 0-66,p<0-01) in most brain regions. However, the relationship between CBF and LCGU in the hippocampus differed significantly from the relationship between the two parameters in the rest of the brain. Thus, the use of the radioactive microsphere method for CBF measurements allows multiple measurements of CBF and permits the assessment of the status of the cerebral vasculature prior to experimental manipulations such as traumatic brain injury. In view of our current findings of an abnormal relationship between CBF and LCGU in cats with high resting CBF levels, this is an important advantage. In addition, the combination of the microsphere and 2-DG techniques within the same tissue samples allows for the investigation of the effects of traumatic injury on the important relationship between CBF and LCGU.