Amyloid b (Ab) is considered to be responsible for the pathogenesis of Alzheimer's disease (AD). Mitochondrial and ER apoptotic pathways are considered to be involved in this process. Galantamine is an acetylcholinesterase (AChE) inhibitor widely used for patients with AD. In this study, we investigated the neuroprotective effects of galantamine on Ab sub(25-35)-induced apoptosis in PC12 cells and the underlying mechanisms. Exposure of PC12 cells to 20 kM Ab sub(25-35) caused significant cell viability loss and apoptosis, Ab aggregation, mitochondrial and ER morphological changes, as well as mitochondrial membrane potential dissipation, reactive oxygen species (ROS) production, intracellular calcium elevation, and cytochrome c release from mitochondria. Pretreatment with 10 kM galantamine for 24 h prior to Ab sub(25-35) exposure significantly reduced Ab sub(25-35)-induced apoptosis not only by preventing Ab aggregation, mitochondrial and ER morphological changes, mitochondrial membrane potential dissipation, ROS production, intracellular calcium elevation, and cytochrome c release, but also via reversing Bcl-2/Bax ratio and suppressing the activity of GADD153, Grp78/94, caspase-9, caspase-12, and caspase-3. All these data indicate that galantamine protects PC12 cells against Ab sub(25-35)-induced apoptosis by preventing mitochondrial dysfunction and endoplasmic reticulum (ER) stress.