A survey of cerebrospinal fluid (CSF) proteins in 334 patients with various neurological disorders was made to judge their relative merit in aiding in the diagnosis of multiple sclerosis (MS). A comparison of direct measurement of CSF IgG by electroimmunodiffusion with estimation of the gamma electrophoretic fraction on concentrated CSF revealed that elevations of the latter correlated better with the diagnosis of MS. That is, the gamma fraction exceeded 14% of the total CSF protein in 94% of MS patients and in only 7.7% of all others. In contrast the IgG fraction exceeded 14% of the total protein in 75% of MS patients and in 23% of all others. Serum immunoglobulins measured at the same time did not differ significantly from one diagnostic category to another.