Pyrogallol (PG) is a polyphenol compound and is known to be an O2*- generator. We evaluated the effects of PG on the growth of human gastric cancer SNU-484 cells in relation to the cell cycle and apoptosis. Dose-dependent inhibition of cell growth was observed in SNU-484 cells with an IC50 of approximately 50 microM following treatment with PG for 72 h. DNA flow cytometric analysis indicated that treatment with PG generally did not induce the specific cell cycle phase arrest. Treatment with 50 microM PG induced apoptosis approximately 20%, as evidenced by sub-G1 cells and annexin V-staining cells. Treatment with PG also induced the loss of mitochondrial membrane potential (Delta psi m) in SNU-484 cells. The intracellular reactive oxygen species (ROS) levels including O2*- were significantly increased in PG-treated cells. Furthermore, the depletion of the intracellular glutathione (GSH) content was observed in cells treated with 50 or 80 microM PG. In conclusion, PG inhibited the growth of human gastric cancer SNU-484 cells by inducing cell cycle arrest as well as triggering apoptosis. The changes in ROS and GSH by PG were closely related to apoptosis in SNU-484 cells.