Astragali Radix has been used in China for more than two thousand years. The main constituents include flavonoids, saponins, polysaccharides, amino acids and trace elements. For centuries in clinical application, Astragali Radix has been prescribed for the treatment of cardiovascular and cerebrovascular diseases, and to enhance endurance and stamina in traditional Chinese medicine (TCM). Many diseases are associated with an imbalance in the regulation of angiogenesis in which there is either excessive or insufficient blood vessel formation, such as various cancers, diabetic retinopathy, stroke and cardiovascular diseases. Astragali Radix is a rich source of novel angiogenic modulating compounds that may reveal previously unidentified angiogenic mechanisms. In an attempt to identify the biological effects of Astragali Radix on angiogenesis and to characterize its underlying mechanisms, the present study investigates the angiogenic effects of Astragali Radix in the following aspects: 1． Isolation of chemical constituents from Astragali Radix: Two Astragali Radix fractions [named Astragali Radix ethanolic fraction (ARE) and Astragali Radix water fraction], five polysaccharide fractions [P1 (MW