OBJECTIVE After exclusion of popliteal artery aneurysms (PAAs) through bypass surgery, there is a risk of persistent flow through collaterals and growth of the excluded aneurysmal sac. This study was conducted to evaluate this risk at long-term follow-up. METHODS Sixty-five PAAs treated by proximal and distal ligation and bypass grafting with reversed autologous vein in 52 patients (1998-2010) were retrospectively reviewed. RESULTS Mean follow-up was 41 months (range, 1-144 months). Five aneurysms showed residual flow (8%). One of these aneurysms had increased in size, 36 months postoperatively. This aneurysm underwent an embolization procedure after which no flow or further enlargement was demonstrated. CONCLUSIONS In this study, the risk of persistent flow in a PAA excluded by proximal and distal ligation and bypass is low. Still, considering this risk and its possible complications, follow-up by duplex ultrasound in all patients until up to more than 10 years postoperatively is recommended.