Pelvic inflammatory disease (PID) may be caused by anaerobic bacteria and/or gonococcus and therefore the efficacy of two antibiotics, ampicillin (AMP) and spectinomycin (SPM) commonly used in this setting was examined against 370 isolates of anaerobic bacteria. At the highest therapeutically achievable serum levels, AMP (16 μg/ml) inhibited 83% of all anaerobes and 70% of Bacteroides fragilis, and SPM (128 μg/ml) inhibited 98% of all anaerobes and 95% of B. fragilis strains tested. It therefore appears that both AMP and SPM may have a place in the treatment of PID. In our study, greater percentage of anaerobes were susceptible to SPM than previously reported. We used the ‘glove box’ technique used for testing the susceptibility of anae