The objective of this study was to determine whether gram‐positive organisms frequently isolated from the periodontium in health and disease contain polyclonal B‐cell activators. Extracts from numerous bacterial strains including Actinomyces viscosus. Actinamyces israelii, Actinomyces NV, Eubacteriun nodatum, Eubacterium brachy, Streptococcus sanguis, Streptococcus anginosus, and Peptostreptococcus micros were tested. All of the organisms contained activity above background, but none of the activators were more potent than pokeweed mitogen, and most were less than half as potent. The aclinomyces appeared to be more active than the eubacteria. streptococci, or peptostreptococci. These PBAs could be significant virulence factors.