Purpose: High glucose concentrations and swings are associated with endothelial dysfunc-tion. We examined the effects of variability in fasting plasma glucose on peripheral artery disease (PAD) in patients with diabetes mellitus (DM). Patients and Methods: In this screening study for the risk factors of PAD, we retrospectively collected data on the ankle-brachial index (ABI) and the percentage of mean arterial pressure (% MAP) at the ankle between August 01, 2016 and July 31, 2017. We defined low ABI <= 0.90, high % MAP >= 45%, or both as high-risk PAD and others as low-risk PAD. We compared the standard deviation (SD) of the first fasting plasma glucose data available each year after January 01, 2007. Results: In 2577 patients, a higher SD of annual fasting glucose was observed in those with an ABI <= 0.90 than in patients with an ABI >0.90 (2.6 +/- 2.1 vs 2.2 +/- 2.3, P = 0.009), and in patients with %MAP >= 45% than in those with %MAP <45% (2.4 +/- 2.1 vs 2.2 +/- 2.3, P = 0.034). A high-risk PAD was significantly associated with the SD (P = 0.032) but not with the mean (P = 0.338) of annual fasting glucose. The former was an independent risk factor for high-risk PAD (odds ratio = 1.424; 95% CI = 1.118-1.814; P = 0.004). Conclusion: Variability but not mean of annual fasting plasma glucose was significantly associated with a high risk of PAD in patients with DM.