Among the recent contributions made by American investigators to our methods for the control of venereal diseases, one of the most important is the precipitation test for syphilis described by R. L. Kahn of the Bureau of Laboratories of the Michigan department of health. Kahn's work has aroused the interest of all who are engaged in the clinical or laboratory diagnosis of syphilis, and it was thought worth while to bring together in some measure the experience of various workers with this method. With this purpose a questionnaire was sent to workers throughout the country who were known to be studying the Kahn reaction. The replies to the inquiry, together with published papers on the same subject, form the basis of this report. First, a word is necessary explanatory of the purpose of study along the lines which Kahn has followed. Since the discovery of the Wassermann reaction in 1906,