In this study, we investigated the effects of linoleic acid (LA), a polyunsaturated fatty acid found in most vegetable oils and certain food products, on the growth of AGS human gastric adenocarcinoma cells. LA treatment resulted in a concentration-dependent growth inhibition of AGS cells by inducing apoptosis, as evidenced by the formation of apoptotic bodies, chromatin condensation, and the accumulation cells in the sub-G1 phase. LA treatment induced cyclin-dependent kinase inhibitor p21 in a p53-independent manner; however, this compound did not affect the cell cycle distribution. Reverse transcription-polymerase chain reaction and western blot analyses showed that treating the cells with LA caused the up-regulation of pro-apoptotic Bax expression and the down-regulation of anti-apoptotic Bcl-2 expression. The apoptosis of AGS cells by LA was found to be associated with an elevated Fas and Fas ligand expression in a concentration-dependent manner. Furthermore, a proteolytic activation of caspases (3, 8, and 9), and degradation/cleavage of poly(ADP-ribose) polymerase and phospholipase C-gamma 1 protein were noted in LA-treated AGS cells. The present results indicate that the Fas/Fas ligand pathway might be involved in LA-induced apoptosis of AGS cells.