B Background: caries in Indonesia is still a major dental and oral health problem,with a prevalence of 88.8%. Streptococcus mutans is one of the bacteria that causescaries. The use of natural ingredients to inhibit the growth of bacteria has beenwidely used, one of which is kitchen lemongrass leaves (Cymbopogon citratus)containing active compounds such as essential oils, flavonoids, polyphenols andsaponins are known to have antibacterial activity. The use of lemongrass leaves asan antibacterial in the form of an infusion with the technique of extracting the activecompound using a water solvent is not widely known, however, the infusion is ingreat demand by the public. Objective: For determine the effect of variouslemongrass leaf making infusion techniques on growth S. mutans. Method:Laboratory experimental research in vitro with a research design in the form ofthepost test only control group design by testing the antibacterial activity of the discdiffusion method. The technique for making dry and fresh lemongrass leaf infusionis obtained by soaking and boiling. Chlorhexidine as a positive control and distilledwater as a negative control. Results: The zone of inhibition in negative control isnot formed, control positive has an inhibition zone of 12 mm, for antibacterialactivity in several infusion techniques it shows an inhibition zone between 3.65 -9.95 mm. Conclusion: Formation of inhibition zones S. mutans the best infusionobtained by boiling dried lemongrass leaves for 15 minutes with an inhibition zoneof 9.95 mm.