ABSTRACT Objective: To evaluate the in vitro antibacterial effect of the ethanolic extract of Erythroxylum novogranatense leaf and 2% chlorhexidine against Streptococcus mutans ATCC25175. Material and methods: The antibacterial effect was determined by the susceptibility test using the Kirby-Bauer method. Twenty-three replicates were performed for each treatment (ethanolic extract of the coca leaf at different concentrations and for the 2% chlorhexidine control group). Strains of Streptococcus mutans were seeded on plates containing Mueller Hinton culture medium, discs were placed with the different concentrations of ethanolic extract of the coca leaf, then the plates were incubated at 37 ° C in micro anaerobiosis, the halos being measured with A millimeter rule after 24 hours. Results: The inhibition halo averages were 8.70; 9.96; 10.96; 13.04; 24.70mm corresponding to the concentratio...