The clinical and computed tomographic (CT) findings in 100 consecutive adult nontraumatic intraventricular hemorrhage (IVH) cases are analyzed. There were 74 parenchymal brain hemorrhages with secondary ventricular extension. The ventricles were filled with blood and asymmetrically enlarged. If the hemorrhage involved putamen, cerebellum, pons, or subcortical cerebral hemispheric white matter, IVH was associated with large parenchymal hematomas; these patients had poor clinical outcome. With thalamic or caudate hematomas, IVH frequently occurred with large hematomas but may occur with small hematomas. The small hematomas were located directly contiguous to the ventricular walls and caused extensive ventricular blood. Patients with small thalamic and caudate hemorrhage with intraventricular blood had good clinical outcome; whereas patients with large hematomas had poor outcome. Primary IVH occurred in 24 cases. In these cases, blood was seen in all ventricular chambers. Aneurysms involving the anterior cerebral-anterior communicating artery region were the most common etiology for primary IVH.