We have treated 12 popliteal aneurysms in ten patients from 1965 to 1989. There were seven men and three women, aged 34 to 78 years (mean, 61.5 years). Two patients had bilateral aneurysms. The chief complaint was pain at rest, claudication, coldness, etc. in eight patients, a mass or induration at the popliteus in two patients, peroneal nerve or vein compression in one patient each. Angiography showed thrombotic obstruction in six legs and distal occlusion in one leg. Ten of aneurysms of eight patients were treated surgically. In two patients, the operation was done on emergency basis. Amputation was not necessary in any case. The operative method was usually excision of the aneurysm. Reconstruction was made with artificial vessels in the first patient who underwent bilateral aneurysm surgery. Auto-saphenous vein were used in other seven patients. All vein grafts were patent at follow-up (mean follow-up period, 4 years and 3 months). Arteriosclerotic changes were histologically observed in all aneurysms. Complications such as thrombotic obstruction and distal occulsion are frequent and leg amputation is necessary in some cases. Arterial reconstruction with an auto-saphenous vein is necessary for popliteal aneurysm.