Senile plaques, one of the principal pathological hallmarks of Alzheimer's disease (AD) consist of a dense core of an aggregated amyloid b-peptide (Ab). A 42 KDa peptide (Ab1-42) is neurotoxic, cosing dendritic injury, sinaptic lose and neuronal death.Induces mitochondrial injury and formation of free radicals. We explored apoptosis-induced by Ab1-42 and its effect on mitochondria and lysosomes in comparison with its non toxic analogue, Ab40-1, in PC12 cells differentiated to neurons. After 6h incubation with the Ab peptides the cells were treated with: lisotracker, mitotracker, Annexin V (apoptosis detection) and propidium iodide (PI, necrosis detection). Cell fluorescence and morphology were determined by confocal microscopy. Neurotoxic Ab1-42 induced significant increase in cell death, both apoptosis and necrosis. Ab1-42 caused mitochondrial aggregation, while Ab40-1 did not. Furthermore, lower fluorescence intensity of lysosomes observed in Ab1-42cells, is probably due to lysosomal rupture. Our results suggest that mitochondria aggregation and lysosome rupture are involved in Ab-toxicity and that it is induced by means of mitochondrial impairment.