The efficacy and safety of two antibiotic combination (clindamycin + gentamycin [C + G] versus metronidazole + gentamycin [M + G]) have been compared in 45 in-patients suffering from pelvic inflammatory disease in a clinical prospective randomized trial. The rates of clinical and bacteriological recovery reached respectively 85.7% and 71.4% for C + G group compared to 83.3% and 78.6% for M + G group (no significant differences). Side effects (vomiting, gastralgia and vaginal mycosis) developed in four occasions in each group. The most frequently isolated organisms were chlamydiae, E. coli and Neisseria gonorrheae (around 50% of overall isolated organisms). Due to the lack of significant differences between the two antibiotic combinations, the final choice will depend on potential risks generated by these products.