I. In the cases diagnosed clinically as cerebrospinal syphilis the Wassermann reaction upon the spinal fluid was always positive and the colloidal gold test showed a reaction in the paretic zone.II. In paresis the colloidal gold test was always found positive in cases where the spinal fluid showed a similar reaction to the Wassermann test, in addition to which there is one instance noted in which the fluid Wassermann was negative, but a reaction in the luetic zone obtained by the gold solution.III. In dementia præcox, manic-depressive insanity, arteriosclerotic dementia and epilepsy there were no positive Wassermann reactions upon the fluid, and likewise no response to the gold solution in the typical "paretic zone". However, the latter reagent did furnish in eight cases of the 152 examined a reaction within the minor limits of the "luetic zone."IV. In the unclassffied psychoses the calloidal gold and the Wassermann reactions upon the fluid ran a parallel course, except in one case, which showed a negative response to the Wassermann test upon the fluid, but gave a gold reaction in the "paretic zone." This instance is clinically a possible case of paresis.V. From our work the opinion is drawn that the colloidal gold reaction forms a useful adjuvant to the Wassermann, is apparently as reliable and, in some instances, by reason of positive response in the absence of the Wassermann in clinically luetic cases, has seemed to point towards the possible appearance of a later positive Wassermann in the suspected individuals.