Cisplatin activates multiple signal transduction pathways associated with cell survival and apoptosis in various cell types. The present study was undertaken to determine the role of extracellular signal-regulated protein kinase (ERK), a member of the mitogen-activated protein kinase family, in cisplatin-induced apoptosis in human glioma cells. Cisplatin resulted in apoptosis in a dose- and time-dependent manner. Cisplatin-induced apoptosis was prevented by the hydrogen peroxide scavenger pyruvate and the antioxidant N-acetylcysteine, but not by the superoxide scavenger tiron. Western blot analysis demonstrated that cisplatin treatment induced time-dependent activation of ERK, which was inhibited by chemical inhibitors of the MEK signaling pathway (PD98059 and U0126) and N-acetylcysteine. These inhibitors prevented cisplatin-induced cell death. Transient transfection of constitutive active MEK1 increased cisplatin-induced apoptosis. Cisplatin resulted in a reduction in mitochondrial membrane potential and its effect was prevented by N-acetylcysteine and PD98059. Caspase inhibitors (Boc-D-FMK and zDEVD-FMK) protected against cisplatin-induced cell death. Cisplatin-induced activation of caspase-3 was inhibited by N-acetylcysteine and PD98059. Taken together, these findings suggest that the ERK activation plays an active role in mediating cisplatin-induced apoptosis of human glioma cells and functions upstream of mitochondrial dysfunction and caspase activation to the initiate the apoptotic signal.