Abstract: Xiaoaiping, extracted from Marsdenia tenacissima (Asclepiadaceae), is a Chinese medicine used to treat cough and asthma. Previous studies have shown that its active ingredients possess anti-inflammatory and anticancer effects. The aim of this study was to investigate the antitumor activities of Xiaoaiping through apoptosis induction in human gastric cancer SGC-7901 cells. The MTT assay was used to assess the cell growth and cell viability. SGC-7901 cells were treated with Xiaoaiping injection (20-40) mgmL-1 for 24 and 48 h. The apoptotic cells and the cell cycle distribution were analyzed by flow cytometry. The in vivo activity of Xiaoaiping was determined by the growth inhibition of the established tumor xenografts in nude mice. Caspase-3 activity, Bax and Bcl-2 proteins in tumor tissue were measured by immunohistochemistry and apoptosis was assayed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) method. Xiaoaiping inhibited SGC-7901 cell growth in a time and dose dependent-manner and the estimated IC50 was (38.20 0.27) mgmL-1 after 24 h of treatment. The body weight and the tumor volume were significantly reduced in nude mice bearing human gastric tumor treated with Xiaoaiping. The inhibition rate of tumor growth in the mid-dose (200 mgkg-1) group and high dose (400 mgkg-1) group were 61.19% and 69.07%, respectively. Immunohistochemical staining showed an increase in caspase-3 and Bax expression whereas Bcl-2 expression decreased gradually. Xiaoaiping exerted potent antitumor activity in vitro and in vivo against human SGC-7901 cells; induced apoptosis and G1 cell cycle arrest. These results suggest that Xiaoaiping is a promising antitumor agent for the treatment of human gastric cancer.