Recent reports that habitual marathon runners demonstrate higher levels of stiffness and cardiovascular risk factors have been of great interest to the medical and scientific community. Ultra-marathon running, that is any distance >42.2 km, is increasing in popularity; however, little is known regarding the physiological effects of the sport's unique training and racing practices on vascular health. OBJECTIVE To characterize and compare the arterial compliance of male long-term (>5 years) ultra-marathoners with recreationally active controls, and examine the associations of training related practices with systemic arterial compliance. METHODS We employed a case-control comparison design using long-term habitual ultra-marathon runners (n=18) and an age matched cohort of normative recreationally active males. METHODS Arterial compliance was measured at rest using radial applanation tonometry (CR-2000, HDI) for diastolic pulse contour analysis. Compliance was compared with normative data, participant characteristics, and associated exercise parameters. RESULTS In representative ultra-endurance runners, large artery compliance of long-term participants was reduced compared with physically active age-matched controls (p=0.03) and is related to select training variables. Specifically, in a representative subset for whom we obtained detailed training data, decreased compliance was related to longer typical running distance per training session (r=-0.72, p=0.03); however, more broad definitions of frequency, intensity, and duration revealed no association for the runners as a whole. CONCLUSIONS Given the known associations of arterial stiffness with future cardiovascular events, ultra-endurance runners may be at an increased risk of a cardiovascular event compared with their normally active counterparts.