Abstract. 20(S)-ginsenoside rg3 [20(S)-rg3)], one of the main constituents isolated from Panax ginseng, has been shown to have an anti-cancer effect and to induce apoptosis by interfering with several signaling pathways. However, the molecular mechanisms of aMP-activated protein kinase (aMPK) associated with apoptosis in HT-29 colon cancer cells remain unclear. in the present study, we investigated whether 20(S)-rg3 exerts an anti-proliferative effect and induces apoptosis by modulating the aMPK signaling pathway in HT-29 cells. 20(S)-rg3-treated cells displayed several apoptotic features, including dna fragmentation, proteolytic cleavage of poly (adP-ribose) polymerase (ParP) and morphological changes. 20(S)-rg3 downregulated the expression of anti-apoptotic protein B-cell cll/lymphoma 2 (Bcl2), up-regulated the expression of pro-apoptotic protein of p53 and Bcl-2-associated X protein (Bax), and caused the release of mitochondrial cytochrome c, ParP, caspase-9 and caspase-3. However, 20(S)-rg3-induced apoptosis was completely abolished in the presence of compound c (aMPK inhibitor) or small interfering rna for aMPK (siaMPK). in addition, STo-609 (caMKKβ inhibitor) attenuated 20(S)-rg3-induced aMPK activation and apoptosis. These results suggest that 20(S)-rg3-induced apoptosis in HT-29 cells is mediated via the aMPK signaling pathway, and that 20(S)-rg3 is capable of inducing apoptosis in colon cancer.