Background: aB-crystallin is a chaperone protein and a potential myelin antigen to human T cells in Multiple Sclerosis (MS). In this study we investigate the existence of aB-crystallin in the cerebrospinal fluid (CSF) of patients with clinical symptoms of MS and control individuals without these symptoms, using a newly developed aB-crystallin specific chicken antibody. Methods: A chicken anti-aB-crystallin was raised against recombinant aB-crystallin, characterized and used in a semiquantitative Western blot analysis of CSF from 16 MS patients and 16 neurological patients without MS. Results: Western blot analysis revealed the presence of high molecular weight aB-crystallin in CSF. Possibly posttranslationally modified aggregates of aB-crystallin were found in human astroglioma U373 cells. CSF aB-crystallin was seen in the CSF in 100% of MS patients and 88% of neurological controls without MS. Conclusion: aB-crystallin is present in the CSF in patients with MS and other neurological controls. Furthermore, aB-crystallin in CSF and human astroglioma cell line U373 is found in aggregates.