ANEURYSMS OF ANY size involving the A1 segment of the anterior cerebral artery are unusual, but giant aneurysms in this location are exceedingly rare, with only five cases previously reported in the literature. We report three cases of A1 segment giant aneurysms presenting with mass effect that were successfully treated. A discussion of the salient features of diagnosis and treatment are presented, along with a brief review of the literature describing these aneurysms. The role of newer imaging modalities, including magnetic resonance imaging, magnetic resonance angiography, and intraoperative angiography, is discussed. The three patients were treated by direct exploration, trapping, and endaneurysmal decompression. Giant A1 segment aneurysms present a unique opportunity to safely trap and decompress the aneurysm with definitive cure.