IN THE fluorescent treponemal antibody (FTA) procedure, as in other serologic tests for syphilis, difficulties have been encountered in increasing sensitivity without sacrificing specificity (1). Recent findings by immunofluorescent methods suggest that a major cause, of nionspecificity in the FTA test may be the occurrence of common or group antigens shared by bot,h pathogenic and saprophytic treponemes. Demonstrations that the corresponding nonspecific antibodies can be removed by appropriate absorption procedures suggested the application of principles that have resulted in an improved FTA test designated as the FTA absorption procedure (FTA-ABS). Its sensitivity and specificity were determined by testing critical categories of selected human serums, using severa.l PTA test procedures and the Treponerna pallidunim immobilization (TPI) test.