Oxidative stress, caused by an imbalance in redox states, involves excessive reactive oxygen species (ROS) or dysfunction of the antioxidant system. The brain is particularly vulnerable to ROS due to its high oxygen demand and lipid-rich cells. Oxidative stress plays a central role in neurodegenerative diseases like Alzheimer's and Parkinson's. Antioxidant therapy has been proposed for prevention and treatment, but results have been inconsistent. This review discusses the role of oxidative stress in neurodegenerative diseases, methods to measure oxidative damage, and current antioxidant treatments. ROS are generated through various pathways, including mitochondrial respiration and NADPH oxidases. Antioxidants such as SOD, glutathione peroxidases, catalase, and peroxiredoxins help neutralize ROS. GSH is a key endogenous antioxidant in the brain. Vitamin E and C are also important antioxidants. Oxidative stress is linked to mitochondrial dysfunction, protein misfolding, and DNA damage. In Alzheimer's, Aβ accumulation increases oxidative stress, while in Parkinson's, mitochondrial dysfunction and α-synuclein aggregation contribute to oxidative stress. Measurement of oxidative stress in the brain is challenging, but techniques like magnetic resonance spectroscopy and positron emission tomography are being used. Antioxidant therapy has shown promise in animal studies but has been ineffective in clinical trials due to factors like insufficient dose, timing, and individual variability. Future research should focus on developing better biomarkers and combination therapies for neurodegenerative diseases.Oxidative stress, caused by an imbalance in redox states, involves excessive reactive oxygen species (ROS) or dysfunction of the antioxidant system. The brain is particularly vulnerable to ROS due to its high oxygen demand and lipid-rich cells. Oxidative stress plays a central role in neurodegenerative diseases like Alzheimer's and Parkinson's. Antioxidant therapy has been proposed for prevention and treatment, but results have been inconsistent. This review discusses the role of oxidative stress in neurodegenerative diseases, methods to measure oxidative damage, and current antioxidant treatments. ROS are generated through various pathways, including mitochondrial respiration and NADPH oxidases. Antioxidants such as SOD, glutathione peroxidases, catalase, and peroxiredoxins help neutralize ROS. GSH is a key endogenous antioxidant in the brain. Vitamin E and C are also important antioxidants. Oxidative stress is linked to mitochondrial dysfunction, protein misfolding, and DNA damage. In Alzheimer's, Aβ accumulation increases oxidative stress, while in Parkinson's, mitochondrial dysfunction and α-synuclein aggregation contribute to oxidative stress. Measurement of oxidative stress in the brain is challenging, but techniques like magnetic resonance spectroscopy and positron emission tomography are being used. Antioxidant therapy has shown promise in animal studies but has been ineffective in clinical trials due to factors like insufficient dose, timing, and individual variability. Future research should focus on developing better biomarkers and combination therapies for neurodegenerative diseases.