We report a case of spontaneous regression of a cystic adventicial dis
ease of a popliteal artery in a 37 years old man. The peroperative res
ection of the adventicia give us the histologic confirmation of the di
agnostic. The cyst's content may have gone through either in the peri-
arterial space or through a communication with the articulation of the
knee. For us, it seems to confirm the embryologic theory for the path
ogenic of this disease.