BACKGROUND Although angiography is still gold standard for the diagnosis of cerebral aneurysms, false-negative angiograms in cases of subarachoid hemorrhage due to a rupture of an anterior communicating artery aneurysm have been previously reported. We now report a case of an anterior communicating aneurysm demonstrated by 3-dimensional digital angiography (3D-DSA) after a negative standard angiogram. CASE DESCRIPTION A 41-year-old female was admitted in a comatose state. Computed tomography (CT) revealed intraventricular hemorrhage and a clot in the frontal interhemispheric fissure, suggestive of rupture of an anterior communicating artery aneurysm. Two days later, angiography was performed. Although standard 3-vessel angiogram with multiple views, using cross-compression on each carotid artery, was negative, 3D-DSA revealed an anterior communicating aneurysm. The aneurysm was successfully clipped based on the findings obtained from the 3D-DSA. The outcome was favorable, with mild memory disturbance. CONCLUSION The standard angiogram sometimes fails to demonstrate aneurysms, especially those on the anterior communicating artery. In this case, 3D-DSA was useful for the diagnosis of the anterior communicating aneurysm which was not seen on standard angiogram. (C) 2002 by Elsevier Science Inc.