Pelvic inflammatory disease (PID) is a polymicrobial infection that evolves multiple aerobic and anaerobic bacteria. Several of the bacterial pathogens that participate in PID can produce the enzyme beta lactamase. These include Bacteroides species (including Bacteroides bivius, Bacteroides disiens, and Bacteroides fragilis group), Neisseria gonorrheae, Enterobacteriaceae and Staphylococcus aureus. A recent increase in numbers of beta-lactamase-producing strains of these organisms in PID has been associated with increased failure rates of penicillins in eradication of this infection. These organisms cannot only survive penicillin therapy but also protect penicillin-susceptible pathogens from the drug. These direct and indirect virulence characteristics of beta-lactamase-producing bacteria require the administration of appropriate antimicrobial therapy directed against all of these pathogens in the therapy of PID.