['Vascular function is impaired in patients with diabetes, however diabetic vascular dysfunction is ameliorated by exercise training. We aimed to clarify which hindlimb arterial segments are affected by treadmill running in the hindlimbs of streptozocin-induced type 1 diabetic mice in vivo.', 'Mice were divided into 3 groups; healthy control, diabetic control, and diabetic-running groups. The exercise regimen was performed by treadmill level running mice for 60\xa0min/day, for 4\xa0weeks. Thereafter, we examined the vascular response to systemic acetylcholine administration in the left hindlimb of anesthetized-ventilated mice using either 1) X-ray microangiography to visualize the arteries or 2) ultrasonic flowmetry to record the femoral arterial blood flow.', 'X-ray imaging clearly visualized the hindlimb arterial network (~70-250\xa0μm diameter). The vasodilator response to acetylcholine was significantly attenuated locally in the arterioles <100\xa0μm diameter in the diabetic group of mice compared to the control group of mice. Post-acetylcholine administration, all groups showed an increase in hindlimb vascular conductance, but the diabetic mice showed the smallest increase. Overall, compared to the diabetic mice, the treadmill-running mice exhibited a significant enhancement of the vasodilator response within the arterioles with diabetes-induced vasodilator dysfunction.'] Does treadmill running improve hindlimb arteriolar endothelial function in type 1 diabetic mice as visualized by X-ray microangiography?