Oxidative stress is implicated in neuronal death in a variety of neurodegenerative diseases. In the present study, P19 neurons obtained by the differentiation procedure from mouse teratocarcinoma P19 cells were used to investigate the ability of quercetin, a plant-derived flavonoid, to prevent neuronal death induced by exposure to 150 μM or 1.5 mM hydrogen peroxide (H(2)O(2)) for 24 h. Quercetin treatment improved viability of P19 neurons exposed to both types of oxidative injury. During the modest oxidative stress, quercetin diminished generation of reactive oxygen species (ROS) and prevented H(2)O(2)-induced nuclear condensation, increase in caspase 3/7 activity and rise in poly(APD-ribose) polymerase expression. Expression of Bcl-2 family members Bax and Bcl-2 was not affected by quercetin treatment at both the transcriptional and translational levels. During the severe oxidative injury, quercetin prevented H(2)O(2)-induced rise in ROS accumulation and changes in plasma membrane integrity and nuclear morphology. The obtained results suggest that neuroprotective effects of quercetin are related to its antioxidative action and prevention of events associated with programmed cell death cascade. In the light of these findings, one might assume beneficial effects of quercetin for the prevention of oxidative stress-driven neuronal loss in human aging and age-related neurodegenerative diseases.