The short-chain fatty acid (SCFA) butyrate is known to induce apoptosis in colon cancer cells in vitro and in vivo, however, its mode of action is poorly defined, whilst less is known regarding the effects of the SCFA propionate. This study investigated the potential for butyrate and propionate to alter cell viability, cell cycle regulation and intracellular protective mechanisms in a human gastric cancer cell line (Kato III). Kato III cells were incubated with butyrate or propionate for 24, 48 and 72 hr. At each time point, cells were assessed for the induction of apoptosis and cell cycle alterations using flow cytometry. Oxidative pentose pathway (OPP) activity and glutathione (GSH) availability were also measured as an index of intracellular protection. Butyrate and propionate differentially induced apoptosis and necrosis in Kato III cells and arrested cells in the G2-M phase. OPP activity was significantly increased by both SCFAs although butyrate induced a 10-fold greater increase than propionate. GSH availability was significantly decreased in Kato III cells by butyrate and propionate. These findings demonstrate that butyrate and propionate induce apoptosis and cell cycle alterations in Kato III gastric cancer cells. Moreover, the effects of butyrate were significantly greater than propionate. We propose that alterations to intracellular redox state and GSH availability play an important role in SCFA-mediated cell death in this cell type. The inclusion of butyrate and propionate as adjunctive cancer therapies has the potential to enhance the efficacy of current chemotherapeutics in the treatment of gastric cancer.