Abstract The oral cavity harbors a rich and diverse microflora, which is mostly found within biofilms attached to the various soft- and hard-tissue surfaces. Recent studies using molecular methods have revealed previously unrecognized species within biofilms associated with health and several common oral diseases. These unrecognized species established an under-appreciated diversity within the flora, with new questions to be answered. Information regarding the composition of the oral microbiome associated with oral health, dental caries, periodontal disease, and endodontic infection is briefly reviewed. Recent concepts regarding the potential role of the oral microbiome in several common systemic diseases are also briefly discussed.