To investigate the role of mitogen-activated protein kinase (MAPK) and downstream events in cadmium (Cd)-induced neuronal apoptosis executed via the mitochondrial apoptotic pathway, this study used the PC-12 cell line as a neuronal model. The result showed that Cd significantly decreased cell viability and the Bcl-2 / Bax ratio and increased the percentage of apoptotic cells, release of cytochrome c, caspase-3, and poly(ADP-ribose) polymerase cleavage, and nuclear translocation of apoptosis-inducing factor (AIF) and endonuclease G. In addition, exposure to Cd-induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. Inhibition of ERK and JNK, but not p38 MAPK, partially protected the cells from Cd-induced apoptosis. ERK and JNK inhibition also blocked alteration of the Bcl-2 / Bax ratio and cytochrome c release and suppressed caspase-3 and poly(ADP-ribose) polymerase cleavage and AIF and endonuclease G nuclear translocation. Taken together, these data suggest that the ERK- and JNK-mediated mitochondrial apoptotic pathway played an important role in Cd-induced PC12 cells apoptosis.