1. Hydrogen sulphide (H(2)S) is a well-known cytotoxic gas. Recently, H(2)S has been shown to protect neurons against oxidative stress caused by glutamate, peroxynitrite and HOCl. Considerably lower H(2)S levels have been reported in the brain of Alzheimer's disease (AD) patients with accumulation of beta-amyloid (A beta). 2. The aim of present study was to explore the cytoprotection by H(2)S against A beta(25-35)-induced apoptosis and the molecular mechanisms underlying this effect in PC12 cells. 3. Our findings indicated that A beta(25-35) significantly reduced cell viability and induced apoptosis of PC12 cells, along with dissipation of the mitochondrial membrane potential (MMP) and overproduction of reactive oxygen species (ROS). 4. Sodium hydrosulphide (NaHS), an H(2)S donor, protected PC12 cells against A beta(25-35)-induced cytotoxicity and apoptosis not only by reducing the loss of MMP, but also by attenuating the increase in intracellular ROS. 5. The results of the present study suggest that the cytoprotection by H(2)S is related to the preservation of MMP and attenuation of A beta(25-35)-induced intracellular ROS generation. These findings could significantly advance therapeutic approaches to the neurodegenerative diseases that are associated with oxidative stress, such as AD.