The fluorescent antibody (FA) capabilities of several laboratories have been joined in collaborative research intended to develop FA reagent grade conjugates specific for certain plaque streptococci and filaments. The prevalence of certain plaque organisms has been determined using both FA methods and conventional cultural methods to estimate the reliability of each method. The purpose of the present study is to provide identification methods and criteria to permit the accurate enumeration of plaque streptococci and certain other plaque organisms considered to be cariogenic. Colored plates have been prepared to portray representative colonial types of each serotype of Strep. mutans, other oral streptococci and selected plaque bacteria. Tabular summaries of the biochemical and physicological characteristics distinguishing each of these plaque bacteria are being prepared. Efforts in fluorescent antibody research have resulted in the development of improved immunization schedules and higher titered antisera.