In order to investigate the pharmacological properties of fractions of Astragali Radix and Polygalae Radix, the effects of the fractions on cerebral ischemia and subsequent reperfusion were studied. Brain ischemia was induced by bilateral common carotid artery occlusion in mongolian gerbil. Brains were recirculated for 30 mins after the 20 min occlusion. Methanol and butanol fractions of Astragali Radix and Polygalae Radix were administered orally 2 hrs before common carotid artery occlusion. Histological observations showed that brain ischemia induced severe brain damage evidenced by the presence of necrotic foci, edema and hemorrhage. This injury was prevented by the methanol fraction and butanol fraction of Polygalae Radix. The level of ATP in brain tissue significantly decreased in ischemic gerbils. This decrease was prevented by the pretreatment with butanol fraction of Polygalae Radix. In contrast, the levels of lactate and lipid peroxide were both elevated in ischemic gerbils. This elevation was inhibited by the pretreatments with methanol fraction and butanol fraction of Polygalae Radix. Our findings suggest that the Polygalae Radix improves ischemia-induced brain damage.