Regional cerebral blood flow was determined using the tracer [14C]iodoantipyrine and regional brain dissection, and regional cerebral glucose utilization determined using the 2-deoxyglucose method, in the alpha-chloralose-anesthetized cat to evaluate the effect of electrical stimulation of the sphenopalatine (pterygopalatine) ganglion. Unilateral stimulation for either a short period (7-10 min) or a longer period (45 min) resulted in increases in blood flow in the ipsilateral cerebral cortex of up to 45% (parietal cortex) with, in addition, increased flow in the white matter of the corpus callosum (42%). The flow changes for both brief and prolonged stimulation were not significantly different. Flow was not altered in either the brainstem or basal ganglia (caudate nucleus). In contrast to these changes in cerebral blood flow no changes in cerebral glucose utilization were seen in any of the brain areas studied and in particular there were no changes in the areas in which blood flow increased. These data provide clear evidence that the innervation of the cerebral vasculature from the main parasympathetic ganglion can alter cerebral blood flow independent of cerebral metabolism.