Objective : Successful coil embolization of anterior communicating (A-com) artery aneurysms requires good visualization and understanding of the entire H complex. Bilateral carotid angiography may optimize anatomical understanding and visualization of the H complex. We therefore assessed the efficacy of simultaneous bilateral internal carotid angiography during coil embolization for A-com artery aneurysms. Methods : Of the 153 patients with intracranial saccular aneurysms who underwent embolization between July 2008 and December 2009, 12 had A-com artery aneurysms and were embolized under bilateral carotid angiography. Patients were evaluated angiographically, immediately and 6 months (n=11) after embolization, using a 3-point scale (complete, residual neck, residual aneurysm). The safety, performance and efficacy of this approach were retrospectively evaluated. Results: In all patients, bilateral internal carotid artery angiography provided more detailed anatomical information and understanding around the A-com artery, and, in complex situations, it allowed for more effective coil embolization through bilateral routes to the A-com artery. Angiography immediately after embolization showed occlusion of 11 of the 12 (92%) aneurysms, with none of these 11 showing evidence of recanalization at 6 months. Conclusion : These findings indicate that simultaneous bilateral carotid angiography during coil embolization of selected complex A-com artery aneurysms provided improved anatomical understanding, and resulted in more effective and safer procedures than typical unilateral angiography.