1. Introduction Types of reactive oxygen species (ROS) Sources Structure Mechanism of ROS generation p53,oxidative stress and ROS. 2. Oxidative stress and free radical damage Oxidative lipid damage Oxidative DNA damage Oxidative protein damage Role of ROS in cell signaling Aberrant regulation of redox-sensitive signal pathway Molecular mechanism of age-related diseases. 3. Antioxidant defense Antioxidant therapy Oxidative modification of protein and possible biomarkers. 4. Specific pathways transduced by ROS and ROS-induced apoptosis will provide opportunities to impact both life span, Age related-diseases and design the chemotherapeutics for humans.