SEVERAL methods for quantitation of serum immunoglobulins (γG, γA, γM, and γD) have recently been developed,1-3 and they have aided in the diagnosis of various diseases. Since changes in the concentrations of proteins in cerebrospinal fluid (CSF) are known to occur in a variety of neurological diseases, similar absolute quantitation of the CSF immunoglobulins would be desirable. During the past few years CSF immunoglobulin evaluation has been primarily qualitative. Lattere et al4 have shown that most of the immunoglobulins of CSF have the same antigenic determinants as do serum immunoglobulins. Stastny et al5 has found that γG is the principal immunoglobulin of CSF. With these facts in mind, we have developed a relatively simple method for absolute quantitation of the immunoglobulins in small volumes of unconcentrated CSF. The method is a variation of the antibody-agar technique2,3 commonly used for serum immunoglobulin quantitation. It involves the diffusion