Cerebro-spinal fluid samples from 44 patients were studied by microimmune-electrophoresis for the presence of [alpha]1-lipoprotein, [alpha]2-macroglobulin, [beta]-lipoprotein, and fibrinogen. The frequency with which these components were demonstrated in the cerebrospinal fluid varied with their molecular weight and possibly also with the shape of the molecules. a1-lipoprotein and [alpha]1-macroglobulin could be demonstrated even in the absence of any neurologic disease. However, [beta]-lipoprotein and fibrinogen were only found in cerebrospinal fluid samples from subjects with known neurologic disease. Demonstration of blood proteins of macromolec-ular type in the cerebrospinal fluid by microimmunoelectrophoresis may yield valuable information in the diagnosis of neurologic diseases with involvement of the passage of the proteins between the blood and the cerebrospinal fluid. An attempt is made to grade neurologic disorders with the aid of such determinations, hoping to find a sensitive supplementary tool in the examination of the cerebrospinal fluid.