Se evaluó la actividad antimicrobiana de cuatro extractos de propóleos argentinos, cinco colombianos y uno cubano frente a Streptococcus mutans ATCC 25175. La actividad bactericida y bacteriostática fue medida por concentración mínima inhibitoria en un rango entre 0.02 y 15 mg/ml. La totalidad de las muestras analizadas presentaron actividad contra Streptococcus mutans a concentraciones de 15 a 3.75 mg/ml. Los propóleos que presentaron mayor efecto bactericida fueron el 2 y el 3 (muestras colombianas) luego de 48 horas de incubación.El mejor efecto bacteriostático lo presentó la muestra 2 (propóleo colombiano) a un periodo de incubación de 24 horas. El 70% de las muestras de propóleo incrementaron su actividad luego de un tiempo de incubación de 48 horas, en relación con el efecto detectado a las 24 horas. A mayor exposición de las bacterias al propóleo, las muestras colombianas mostraron un efecto superior, las argentinas un efecto moderado y las demás muestras (30%), permanecieron estables.It was evaluated the antimicrobial activity of four propolis extracts from Argentina, five from Colombia and one from Cuba, using Streptococcus mutans ATCC 25175. The samples were kept in a 96% ethylic alcohol solution, remaining a concentration of 3%. The bactericidal and bacteriostatic activity was measured by the minimun inhibitory concentration among a range of 0.02 and 15mg/ml. All of the analyzed samples showed activity against Streptococcus Mutans when they are used to concentrations 15 a 3.75 mg/ml. The propolis that presented the highest effect bactericidal was number 2 and 3 (sample from Colombia) after 48 hours of incubation.The highest effect bacteriostatic was presented by the sample 2 (propolis from Colombia) after 24 hours of incubation. 70% of the propóleo samples increased their activity after a time of incubation of 48 hours compare to the effect shown to the 24 hours. All the Colombian samples showed a superior effect, when the bacteria were exposed to the propóleo for a longer period of time; in two of these cases until of five dilutions, samples 2 and 3, this effect was presented in a moderate way, using the argentine samples 6 and 10 while the other samples (30%) remained steady.