Malondialdehyde (MDA) is one of the better-kwn secondary products of lipid peroxidation, and it can be used in biomaterials as an indicator of cell membrane injury. The first chapter offers an overview of the implications of MDA on oxidative stress, and therefore in neurogenerative diseases, as well as collects information of several natural products that exert beneficial properties on oxidative stress-related diseases by modulating MDA levels. The second chapter in this book focuses on the role of malondialdehyde in the development of insulin resistance in obesity. The chapter also comprehensively summarizes the pathophysiological roles of malondialdehyde and its impact on cognitive function in obesity. The third and final chapter looks at MDA as a marker of lipid peroxidation, in the internal organs of of Wistar rats. MDA is the final product in the lipid peroxidation process, and the degree of lipid peroxidation, oxidative stress, can be evaluated by measuring the level of MDA in different tissues. The potential protective effects of O- and S- dor supplements (glutathione and lipoic acid) on lipid peroxidation effects were described as well.