A review of the literature on orofacial odontogenic infections indicates that the underlying microflora is typically polymicrobial, predominantly involving strictly anaerobic gram-positive cocci and gram-negative rods, along with facultative and microaerophilic streptococci. Although no single species has been consistently implicated in all of these infections, the pathogenic potential of some of these organisms has been documented by many studies. This potential can be explained by a number of virulence factors demonstrated in anaerobic bacteria, as well as by synergistic interrelationships with other members of the infectious flora. Awareness of the anaerobic component of orofacial odontogenic infections dictates to a large extent the selection of antimicrobial therapy, mainly because of the frequency of beta-lactamase production by anaerobic gram-negative rods.