The study was aimed to investigate the effect cuscutae semen(CS) on the vascular systems including changes in blood pressure (BP), regional cerebral blood flow(rCBF) and pial arteriolar diameter of male Sprague-Dawely rats. The changes in rCBF were determinated by laser-Doppler flowmetry, and the changes in diameter of pial arteriole were measured through a closed crainal window. 1. Blood pressure was not affected by CS in rats. 2. rCBF was increased by CS in a dose-dependent manner. 3. Pretreatment with methylene blue(Img/kg), and propranolol(1mg/kg) significantly inhibited CS induced increased in rCBF. 4. Pretreatment with indomethacin(1mg/kg) did not inhibited CS induced increased in rCBF. 5. Pial arterial diameter was increased by CS in a dose-dependent manner. These results suggest that CS causes a diverse response of blood pressure, regional cerebral blood flow(rCBF), and pial arteral diameter. The increased in rCBF is also mediated by adrenergic ${eta}-receptor $ and guanylate cyclase.