Despite advances in diagnosis and treatment, a brain abscess caused by anaerobic micro-organisms still poses a major clinical problem. An experimental model of anaerobic brain abscess in rat was developed to determine the effects of metronidazole and dexamethasone on the abscess thus formed. Rats were inoculated with B. fragilis and treated intraperitoneally each day with either metronidazole (15 mg/kg). dexamethasone (0.25 mg/kg) or both. It was histopathologically shown that a stage of cerebritis preceded capsule formation. When groups were compared, it was observed that the therapeutic doses of metronidazole administered together with dexamethasone was the best treatment.