This study was designed to investigate the effects of Angelicae Gigantis and Cynanchum wilfordii Hemsley extract (AAC) on the changes of regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) in normal rats, and in the rats with cerebral ischemia induced by middle cerebral artery occlusion, and further to determine the mechanisms. The results were as follows. AAC significantly increased rCBF but significantly decreased MABP in a dose-dependent manner in normal rats. The increase of AAC-induced rCBF was significantly inhibited by pretreatment with methylene blue (0.01 mg/kg, i.p.), an inhibitor of guanylate cyclase, and AAC-induced MABP was decreased by pretreatment with methylene blue. In cerebral ischemics, rCBF was stably improved by AAC (10 mg/kg, i.p.) during the period of cerebral reperfusion, which was contrasted with the findings of rapid and marked increase in the control group. These results suggest that AAC can increase rCBF in the normal state, as well as improve the stability of rCBF in cerebral ischemic state.