A case is reported of a brain abscess, which ruptured into the lateral ventricle and was treated using intraventricular irrigation with antibiotics. A 37-year-old man was suffering from a headache and high fever. Precontrast CT scan revealed a heterogeneous low density area in the left temporal lobe, and postcontrast CT scan showed a multilobular ring-like enhanced mass. Diagnosed as a brain abscess, intravenous administration of antibiotics was performed. On the sixth day the patient suddenly became drowsy. Postcontrast CT scan revealed an enhanced effect in the left lateral ventricular wall. Drowsiness was attributed to increased intracranial pressure and severe ventriculitis. Bilateral continuous ventricular drainage via the anterior horn of the lateral ventricle was performed. The drainage fluid from the left lateral ventricle was just like pus. Intraventricular irrigation with antibiotics between the bilateral anterior horns of the lateral ventricle, was performed in order to save the patient. The infusion fluid, Lactate Ringer's solution containing Cefazolin sodium, was infused into the right ventricle and CSF-like pus was drained from the left ventricle. The CSF reading gradually improved, and on the 14th day postoperatively irrigation was terminated. The postoperative course was uneventful. The diagnosis, treatment, and prognosis of patients with brain abscesses have improved dramatically as a result of more reliable methods of identifying infecting organisms, more effective antibiotic regimens, the development of microsurgical techniques and CT scan. However, despite these advances, the prognosis for brain abscess ruptured into the ventricle is usually very pessimistic.(ABSTRACT TRUNCATED AT 250 WORDS)