Specificity is the most important of all requirements of any diagnostic procedure. A serologie reaction for syphilis is not an exception to this rule, and the importance of its specificity in the presence of nonsyphilitic pathologic conditions cannot be overemphasized. The specificity of the Wassermann reaction has long been studied, and it was early learned that false positive reactions were obtained in a great variety of nonsyphilitic conditions, especially in the febrile diseases. As the technic of the complement-fixation reaction was improved, fewer false positive tests were obtained. For example, it is claimed that the modified Wassermann reaction as proposed by Kolmer possesses a high degree of specificity. Kolmer and Steinfield, 1 after examining the reaction with a regard to its specificity, believe that it does not yield false positive results; they are of the opinion that positive tests occurring without clinical or historical evidence of syphilis indicate latent syphilis and demand careful study of the patients concerned. Since Kahn proposed his flocculation test, in 1922, numerous favorable reports have appeared with regard to the sensitivity and specificity of this test. A composite summary of the more than 170 articles which have thus far appeared would indicate that as workers become more