Group B Streptococcus (GBS) is a common vaginal pathogen, but its interaction with Lactobacillus is controverse. Past studies show no correlation between a decrease of Lactobacillus in the vaginal microbiota and the prevalence of GBS infection in vivo; some in vitro studies show that Lactobacillus gasseri (LG) and Lactbacillus crispatus (LC) can inhibit GBS adhesion to vaginal epithelial cells, but not all studies find the same results. The goal of this study is to evaluate the influence of LC and LG on GBS. In our study, GBS was obtained from healthy pregnant women, we used serotypes Ia, II, III and V. LC and LG were obtained commercially. The first experiment consisted of incubating the microorganisms together in liquid media, afterwards GBS colonies were counted in specific agar. We performed two assays using hela cells: competition and exclusion. Competition assay was performed incubating GBS and LC or LG with HeLa cells in 12-well plates containing coverslips, and exclusion assay consisted in incubating LG or LG with HeLa cells overnight, then GBS was added and incubated again. Coverslips were stained, and the results were observed in the microscope. In the assays involving just the microorganisms, no significant difference was observed on GBS growth. But we found differences in growth within serotypes. In the competition assay, LG and LC increased Serotype III adherence. In the exclusion assay LC inhibited adherence of serotypes Ia, II and III, but increased serotype V; LG inhibited only serotype III and V, but not serotypes Ia and II. We saw that GBS serotypes behave differently even when submitted to the same conditions. The influence that LC and LG have on GBS is different, but results do not show if LC or LG can be used to treat or prevent GBS infection.