It is known that formation of dental caries is caused by the colonization and accumulation of oral microorganisms and extracellular polysaccharides which are synthesized from sucrose by glucosyltransferases of Streptococcus mutans. Actinomyces naeslundii and Staphylococcus aureus are associated with human root caries and some oral mucosa infections, respectively. In this research Streptococcus mutans Ingbritt 1600 exhibiting glucosyltransferase activity was used to test whether different ethanolic extracts of propolis (EEP) inhibit or not the enzyme activity and growth of the bacteria. Antimicrobial activity of EEP against A. naeslundii and S. aureus was also examined. All EEP from various regions in Brazil inhibited both glucosyltransferase activity and growth of S. mutans, A. naeslundii and S. aureus, but one of propolis from Rio Grande do Sul (RS2) demonstrated highest inhibition of the enzyme activity and growth of the bacteria. It was also found that propolis (RS2) contained highest concentrations of pinocembrin and galangin.292143148