This report describes a rare case of a distal anterior choroidal artery aneurysm which developed intraventricular haemorrhage without subarachnoid haemorrhage as shown on computerized tomographic (CT) scan. A 69-year-old hypertensive man suddenly became unconscious. An emergency CT scan showed a severe intraventricular haemorrhage and a small round low-dense lesion within the haematoma at the right trigone. The haematoma with obstructive hydrocephalus made the lateral ventricles larger on the right than on the left. CT scan could not detect any subarachnoid haemorrhage. Right interal carotid angiography revealed a saccular aneurysm at the plexal point of the right anterior choroidal artery. We approached the aneurysm and the small round lesion through the trigone via a right temporo-occipital corticotomy. We could clip the aneurysmal neck and remove the intraventricular haematoma and the papillary cystic mass (corresponding to the small round lesion on CT scan) totally in one sitting. Histological examination revealed the aneurysm to be a true one and the papillary cystic mass to be a choroid plexus cyst.