The authors report five cases of surgically treated giant vertebral artery aneurysm. Two giant serpentine aneurysms were managed with aneurysmectomy, a giant semifusiform aneurysm with trapping and partial aneurysmectomy, and the other two saccular giant aneurysms with clipping. Surgical results were satisfactory in all cases. In particular, the two patients who underwent complete aneurysmectomy showed remarkable improvement after the second procedure of a two-stage operation that consisted of initial proximal occlusion and secondary evacuation of clots in the aneurysm when advanced thrombosis was identified. Aneurysmectomy in a two-stage operation was the best treatment for these partially thrombosed giant aneurysms which completely concealed the distal artery under a tight thinned medulla.