Biofilms are highly structured, hydrated microbial communities containing sessile cells embedded in a self-produced extracellular polymeric matrix (containing polysaccharides, DNA and other components). The formation of biofilms might facilitate certain survival and virulence characteristics under some situations. Several mechanisms have been postulated in the biofilm antimicrobial resistance, which includes; slow penetration of the antimicrobial agent into the biofilm, changes in the chemical micro-environment within the biofilm leading to zones of slow or no growth, adaptive stress responses and presence of a small population of extremely resistant “persister” cells. Biofilm biology has become an expanding field of research and the knowledge accumulated suggests that organisms growing in biofilms develop properties different to those dwelling in the planktonic stage. This review article covers the concept of biofilms and its role in endodontic infections.