Intraneuronal accumulation of amyloid beta-protein (A beta) is believed to be responsible for degeneration and apoptosis of neurons and consequent senile plaque formation in Alzheimer disease (AD), the main cause of senile dementia. Oxidative stress, an early determinant of AD, has been recently found to induce intralysosomal A beta accumulation in cultured differentiated neuroblastoma cells through activation of macroautophogy. Because A beta is known to destabilize lysosomal membranes, potentially resulting in apoptotic cell death, this finding suggests the involvement of oxidative stress-induced macroautophagy in the pathogenesis of AD.