To investigate the mechanism of oxidative stress induced death of PC12 cells, we performed confocal and flow cytometric analysis with a reactive oxygen species (ROS)-specific fluorogen, 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Hydrogen peroxide significantly decreased the number of viable PC12 cells after 24 h. Hydrogen peroxide caused membrane blebbing, nuclear condensation and DNA fragmentation, indicating that the PC12 cells died due to apoptosis. The hydrogen peroxide-triggered apoptosis of PC12 cells was associated with enhanced ROS production in a dose-dependent manner by measuring with C-DCDHF-DA. Nerve growth factor (NGF) and Bcl-2 inhibited the hydrogen peroxide-induced apoptosis of PC12 cells. Neither of them, however, reduced the ROS production in PC12 cells. These data suggest that NGF or Bcl-2 protects PC12 cells from hydrogen peroxide-triggered apoptosis independently from ROS production.