The value of quantitative cerebrospinal fluid γ-globulin determinations as an aid in neurological diagnosis has been well established in recent years. Although an abnormal colloidal gold test indicates a relative increase in cerebrospinal fluid γ-globulin in many cases, colloidal gold curves are abnormal in only about one third of fluids showing a pathological increase in γ-globulin content when the latter is quantitatively determined.1 The immunochemical method of measuring cerebrospinal fluid γ-globulin, described by Kabat, Glusman, and Knaub,2 gives highly reproducible results but has the disadvantage of being somewhat time consuming, and this factor limits its usefulness for routine clinical purposes. The same disadvantage applies to electrophoretic techniques, which, in addition, require the concentration of relatively large volumes of spinal fluid. Another method for estimating cerebrospinal fluid γ-globulin employing zinc sulfate precipitation has been advocated; the zinc sulfate method, however, does not specifically measure γ-globulin, a fact clearly