Oxidative processes are involved in aging as well as the pathogenesis of different degenerative diseases. In the last few years the role of low density lipoprotein oxidation in the development of artherosclerosis and coronary heart disease has become evident. Lipoprotein oxidation in plasma is used as a marker for disease progression. We were interested in the role of lipoprotein oxidation in Alzheimer's disease. For this purpose we developed methods to determine the in vitro oxidizability of cerebrospinal fluid and plasma lipoproteins of Alzheimer patients. In addition we measured the lipophilic and hydrophillic antioxidants, alpha-tocopherol (vitamin E) and ascorbate (vitamin C). Cerebrospinal fluid and plasma lipoprotein oxidation was found to be increased in Alzheimer's patients compared to controls and a corresponding decrease of antioxidant vitamins was found. In a pilot study, in vitro lipoprotein oxidation in cerebrospinal fluid of Alzheimer patients could be delayed by vitamin E and C supplementation. In conclusion these data show that increased lipoprotein oxidation could play an important role in Alzheimer's disease and possibly provide a rationale for the treatment of this disease with antioxidant drugs. The clinical effect of this therapeutical approach remains to be proved in long-term studies.