Free radicals and oxidative stress play a crucial role in the pathophysiology of a wide variety of diseases including cancer and neurodegenerative disorders. Reactive oxygen and reactive nitrogen species can react with biomolecules such as proteins, lipids, nucleic acid, etc. resulting in the formation of protein carbonyls, 3-nitrotyroine, HNE-bound proteins, etc. Such modifications in proteins often lead to functional impairment, and the identification of such oxidatively modified proteins may help in delineating the mechanism of disease 1pathogenesis or progression. In this chapter, we described the protocol for the identification of oxidatively modified proteins, i.e., protein carbonyls and HNE-bound proteins in a given biological sample using three important techniques, i.e., proteomics coupled with mass spectrometry and immunochemical detection. These methods are placed in the context of our studies on Alzheimer's disease.