In the present work, the adhesion of 43 human lactobacilli isolates to mucin has been studied. The most adherent strains were selected, and their capacities to adhere to three epithelial cell lines were studied. All intestinal strains and one vaginal isolate adhered to HT-29 cells. The latter was the most adherent to Caco-2 cells, although two of the intestinal isolates were also highly adherent. Moreover, five of the eight strains strongly adhered to HeLa cells. The binding of an Actinomyces neuii clinical isolate to HeLa cells was enhanced by two of the lactobacilli and by their secreted proteins, while those of another two strains almost abolished it. None of the strains were able to interfere with the adhesion of Candida albicans to HeLa cells. The components of the extracellular proteome of all strains were identified by MALDI-TOF/MS. Among them, a collagen-binding A precursor and aggregation-promoting factorlike proteins are suggested to participate on adhesion to Caco-2 and HeLa cells, respectively. In this way, several proteins with LysM domains might explain the ability of some bacterial supernatants to block A. neuii adhesion to HeLa cell cultures. Finally, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) could explain the good adhesion of some strains to mucin.