Alzheimer’s disease (AD) is a devastating neurodegenerative disorder which is thought to affect 26.6 million individuals worldwide. There is growing concern over a worldwide dementia epidemic that is predicted to develop over the coming decades. The evidence thus far suggests that increased levels of oxidative stress and vascular risk factors are two major contributors, amongst others, to AD development. The thesis aimed to investigate markers of oxidative stress in AD plasma. Moreover, the oxidative status of specific proteins was investigated using both hypothesis driven and proteomic approaches. Results presented in this thesis suggest that global plasma protein oxidation levels are not different when AD and control subjects are compared, but that individual plasma proteins are specific targets for oxidative modification in AD. The thesis explores different methodologies to assess oxidative changes in AD. In addition it demonstrates that emerging novel and powerful mass spectrometry techniques can be employed successfully to identify several proteins modified by oxidation, providing an initial starting point for further investigation.