Three cases of non-traumatic intracavernous aneurysms that gave rise to massive epistaxis and required operative intervention, are reported. This is a rare but serious cause of epistaxis, because delayed diagnosis and management can lead to repeated bleedings and even to death. It is important, therefore, to diagnose the source of epistaxis and treat it as soon as possible. In our three patients, an emergency angiography enabled us to diagnose an aneurysm in the cavernous sinus. These aneurysms were located in the C3 or C4 portion of the internal carotid artery and were 3-5 mm in diameter. The projections of these aneurysms were infero-medial, antero-inferior, and lateral, respectively. All three patients underwent emergent surgery. Neck clipping of the aneurysm was performed in two patients, and gradual occlusion of the internal carotid artery in the third patient. Emergency surgery successfully prevented further episodes of epistaxis in all three patients.