The relationship between cerebral blood flow and glucose utilization was studied in conscious rats using the [14C]iodoantipyrine and [14C]2-deoxyglucose quantitative autoradiographic techniques respectively. Both blood flow and glucose use decreased in parallel in the 38 areas of the brain analyzed following administration of the GABA agonist muscimol, thus maintaining the relationship observed in control rats. The present study offers no evidence for a direct vasodilatatory action for muscimol in the conscious rat, but points to underlying regional metabolic activity as the primary determinant of cerebral blood flow.