Femoral aneurysm commonly has no clinical symptoms but once it appears severe symptoms such as rapture of the aneurysm and necrosis of the lower extremity due to obliteration of the artery are induced. We describe a case of bilateral femoral aneurysms which showed a rapid growing. A 71-year-old male, who has been admitted to our hospital with a diagnosis of early gastric cancer, was accidentally detected to have bilateral femoral aneurysms. The aneurysms rapidly increased in size to 6.5×4.5cm in the right and 10.0×4.5cm in the left side without any symptom during his hospitalization. They were successfully reseced and replaced by Cooley's double velour grafts (8mm in diameter)and his saphenous vein graft. Histological examination of the aneurysmal wall revealed an atherosclerotic change extended to the tunica adventitia and partially destroyed internal elastic lamina. Now four months after the vascular reconstruction, the patient is up and well without complaints.