In this paper, a high prevalence of popliteal artery aneurysm (PA) of 14.2%, was found in men with enlarged aortas at population based screening of 65 year old men. There was no correlation with the diameter of the aorta, but a correlation with the diameter of the iliac arteries was identified, suggesting a subgroup with higher risk of concomitant peripheral aneurysms. The prevalence was quite different depending on three different definitions of PA, pointing out the need for a consensus definition, and a need of follow up studies, to see how these definitions correlate with future growth, complications, and the need for surgery. Background: Data on the prevalence of popliteal artery aneurysm (PA) are scarce and difficult to interpret as the definition differs among papers. The aim was to investigate the prevalence among men with screening detected abdominal aortic aneurysms (!30 mm, AAAs) and subaneurysmal aortic dilatation (25e29 mm, SAA), and to explore whether the existence of a PA correlated with the diameters of the aorta, iliac, and femoral arteries. Methods: In Uppsala, Sweden, a county with 376 000 inhabitants, AAA screening of 65 year old men was initiated in 2006. All men with AAA and SAA also had measurements of the common iliac artery (CIA). The common femoral (CFA), superficial femoral (SFA), and popliteal arteries were evaluated at re-examination, performed after 1e2 years for AAA and five years for SAA. PA was defined as ! 12 mm, or 1.5 times larger than the distal SFA according to the ISCVS/SVS Ad Hoc Committee. The relationships between PA and other vessel diameters were explored. Results: A total of 19 820 65 year old men (84.6%) accepted the invitation to screening between 2006 and 2017. AAA was found in 173 (0.9%), and SAA in 149 subjects (1.1% of those screened 2006e2013, eligible for this study). In the whole cohort, 14.2% of those examined had at least one PA of any size, 3.0% were !15 mm and 2.2% ! 20 mm. There was no difference in PA prevalence between AAA and SAA: 15.9% vs. 12.2% (p ¼ .48). There was no difference in aortic diameter in those with or without PA (p ¼ .46), but there were significant correlations with CIA (p < .001), CFA (p < .001), and SFA (p < .001) diameters. Conclusions: A high prevalence of PA among subjects with screening detected AAA and SAA was found. PA was not correlated with the aortic diameter in this cohort, where all had dilated aortas, while correlations with peripheral and iliac artery diameters were identified.