In a 19-year old man a loculated brain abscess developed in a contusional lesion subsequent to head injury. He remained an inpatient at the hospital during the entire time from trauma to operation. The patient had received dexamethasone because of elevated intracranial pressure, and he was supervised via computerised tomography. Besides pre-operative differential diagnosis, the pathogenesis of this septic complication caused by steroids without antibiotics is discussed in the light of recent literature.