We developed an assay which predicts the antimigraine efficacy of sumatriptan. Our assay is based on two assumptions: (1) electrical stimulation of the trigeminal ganglion mimics the neurogenic inflammatory process and (2) stimulation-induced increases in n. trigeminal caudalis blood flow reflect activation of a large population of neurons. Briefly, the trigeminal ganglion was electrically stimulated for 30 s periods at 1 and 10 Hz before and after administration of saline or the antimigraine compound sumatriptan in chloralose-anesthetized cats. Sumatriptan blunted the increase in blood flow following stimulation of the trigeminal ganglion. These data suggest that the n. trigeminal caudalis blood flow model may be useful in identifying antimigraine compounds.