A solid phase radioimmunoassay is described which employs 125I-protein-A to detect the presence of antibodies against a panel of cellular and soluble central nervous system (CNS) specific antigens coated onto polyvinylchloride Microtiter plates. Serum antibodies from rabbits immunized against myelin, myelin basic protein (MBP), glial acidic fibrillary protein (GFAP), astroglioma cells, and cerebellar cells were easily detected, and high specificity for each antiserum and antigen was also demonstrable. The assay is applicable to cerebrospinal fluid (CSF) from patients with neurological diseases to detect antibodies against CNS-specific antigens. The assay should be useful for examining cell lines derived from CNS tissue for the presence of brain proteins.