In a 61 year-old women, suffering a left calf pain for more 18 months, a diagnosis of cystic adventitial disease of the popliteal artery was confirmed by scanner. At the operation, we found an intramural cyst of the popliteal artery. A total resection of the cyst and of the artery (resection and end to end anastomosis) was performed. Adventitial cystic disease represents 0, 1% of the vascular diseases). The popliteal artery seems to be the most frequent site.