Objectives: The aim of this study was to evaluate the Minimum Inhibitory Concentration (MIC) of three dentifrices Methods: The dentifrices had the following characteristics: lack of fluoride;500 ppm of NaF;1100 ppm of NaF,using follow microorganism for analysis:Staphylococcus aureus,Streptococcus mutans,Enterococcus feacalis and Escherichia coli.The dentifrices' volume were measured through disposable syringes for the preparation of the serial dilutions(1:2 to 1:128) in TBS.The bacteria were cultivated in agar TSA 37ºC/24h.After the preparation of 0.5 model bacteria suspension of Mc Farland, a 10µL sample was transferred for each dilution.The negative controls were incubated in TSB without the addition of the toothpaste. Microorganisms were inoculated in the cultures containing the dentifrices' dilutions;and were then incubated at 37ºC/48h.Since the constituents of the dentifrice in the smallest dilutions become bleary,10µL of each test tube were transferred to Petri dishes containing TSA and then were incubated at 37ºC/48h.Antimicrobial activity for non-fluoride toothpaste could not be observed. Both dentifrice fluoride-containing showed antimicrobial activity for all microorganisms tested. Results: The MIC obtained for the following dilutions for 500 and 1100 ppm of the NaF dentifrice were respectively:S.aureus(4,4),E.feacalis(64,128),S.mutans(4,8)eE.coli(2,2). Conclusion: It is concluded that the non-fluoride dentifrice did not present antimicrobial activity towards the bacteria tested.Both fluoride-containing toothpastes present similar MICs and antimicrobial activity towards the microorganisms tested