For many years psychiatrists have appreciated the clinical value of the Wassermann reaction, not only in diseases of the central nervous system, but in somatic infection in the psychotic and the mentally defective. As a diagnostic test for syphilis, reliance has been placed on this reaction out of proportion, perhaps, to its relative efficiency; sometimes without a full appreciation of the difficulties which the pathologist has to face in rendering the test as accurate as possible, and also of the fact that the results must be interpreted both on clinical and serological grounds. Adding to the difficulties of co-operation between the two groups of observers, there has been the fact that, owing to increased efficiency in anti-syphilitic treatment during the past twenty years, the strength of the reactions to be found serologically has become progressively less marked. Thus, it is inevitable that many of the methods employed hitherto, although at one time satisfactory and reliable, cannot now completely fulfil all the criteria of a reliable test so essential to accurate diagnosis and the control of modern methods of treatment. Further, and of even more importance from the point of view of research and of the necessity of making strict comparison of the results of one laboratory with another, it has been ascertained that very little uniformity of method exists. This lack of cohesion not only reflects upon the efficiency of the routine work and research in mental hospitals, but isolates them as a whole from the Ministry of Health venereal disease centres, in that in very many instances the methods employed could not be strictly compared. From these facts alone it will be seen that sooner or later the time was bound to come when all the requirements of a standard method should be investigated and, from among many excellent techniques, the difficult task be faced of choosing one or a combination of tests that would serve the needs of the clinician and serologist working in the domain of psychiatry. At the time of the inception of the Pathological, Bacteriological and Bio-Chemical Sub-Committee there was current amongst its members a desire that one of the aims of this section of the Research and Clinical Committee should be to investigate this difficult and highly technical problem of standardization. Thus, after the preliminary work of the Sub-Committee on various schemes of research had been initiated, I was asked at the meeting on February 13, 1929, to prepare a memorandum on a standard method of performing the Wassermann test. This report was entirely of a preliminary nature, and intended only to form a basis of discussion. While this was in course of preparation a questionnaire was sent to those mental hospitals undertaking serological work, with a view to ascertaining and contrasting in some detail the methods employed by each. In order that all interests in the various branches of psychiatry should be fully represented, it was unanimously decided that all members of the General Paralysis, Mental Deficiency, and Encephalitis Sub-Committees should be invited to co-operate. Thus, on May 3, 1929, a conjoint meeting was held at Horton Mental Hospital, Epsom, under the chairmanship of Dr. J. R. Lord. In the memorandum I dealt mainly with the work of the three laboratory conferences held under the auspices of the League of Nations in November, 1922, November, 1923, and May, 1928, the latter, held at Copenhagen, being by far the most important in its results and influence upon the researches into the serology of syphilis.