BACKGROUND AND PURPOSE Nontuaumatic primary intraventricular hemorrhage in adults is uncommon. The purpose of this study was to identify clinical features, risk factors, and outcome of primary intraventricular hemorrhage in adults. METHODS We identified computed tomography scans for nontraumatic primary intraventricular hemorrhage performed between 1982 and 1993 at our institutions and reviewed medical records to determine clinical features, risk factors, and outcomes of-these patients. RESULTS Of 14 cases studied, the onset of symptoms was acute in all and the most common symptom was headache (78%), followed by nausea/vomiting (71%), and mental status change (71%). Seizures as well as focal neurologic deficits were uncommon. The associated risk factors were hypertension in 7 cases, aneurysm or arteriovenous malformation in 5, coagulopathy in 1, and fibromuscular dysplasia in 1 case. Five patients died acutely, and all of the survivors returned to functional independence, The patients with lethargy, pupillary and extraocular movement abnormalities, quadriparesis, hydrocephalus, and aneurysmal intraventricular hemorrhage had worse outcomes. CONCLUSION Patients with nontraumatic primary intraventricular hemorrhage present with sudden onset of diffuse neurologic symptoms. The mortality in early phase is high (36%) and the prognosis for survivors is good. Factors correlating with the outcome are discussed.