Oxidative stress is increasingly being recognized as a contributing factor in neurological diseases. The brain is especially susceptible to oxidative damage due to its high lipid content, high energy consumption and low antioxidant defenses. Reactive oxygen species (ROS) can react non-specifically and rapidly with all cellular biomolecules; however, lipids are the major target of free radicals. We are investigating the involvement of a novel class of lipid peroxidation in the brain, i.e., Neuroketals (NKs). NKs are the generated from the ROS action on docosahexenoic acid (DHA) which is highly enriched in the nervous system. NKs are believed to be detrimental to brain function because they adduct to critical proteins. The current study sought to determine the levels of neuroketals in thecerebrospinal fluid (CSF) of multiple sclerosis (MS) patients and establish if these levels correlate with disease activity. CSF was obtained by lumbar puncture or by aspiration from an access-port of implanted pumps from 50 patients with clinically definite MS. Control CSF from 20 patients with other neurological diseases served was also obtained. NK levels in the CSF were measured by ELISA. It was found that the NKlevels were nearly 4-fold higher in the CSF of MS patients as compared to the control CSF (p< 0.001).Current studies aim at better defining the correlation of NK levels in the CSF with disease activity and the underlying pathogenic mechanisms. Our findings suggest that NKs may serve as a novel biomarker of disease activity and oxidative stress in MS and thus warrant further investigation.