OBJECTIVE: To investigate the anticancer actions of dihydrotanshinone I (DHTS) in AGS human gastric cancer cells. STUDY DESIGN: Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Intracellular reactive oxygen species (ROS) levels were determined using flow cytometry. Caspase activities were measured with fluorometric assay. RESULTS: Results from MTT assay showed that DHTS significantly inhibited AGS cell viability in dose- and time-dependent manners. Elevated intracellular ROS levels and increased apoptotic cells were observed in DHTS-treated AGS cells. In addition, activation of caspase-3 and caspase-8, rather than caspase-9, was noticed in DHTS-treated AGS cells. Furthermore, blocking ROS generation with N-acetylcysteine markedly reversed DHTS-induced cell apoptosis. CONCLUSION: All the findings strongly suggest that DHTS can initiate ROS generation and induce oxidative stress and cell apoptosis in AGS human gastric cancer cells, which deserves to be further developed as an anticancer agent. © Science Printers and Publishers, Inc.