Objective.To assess associations between cardiorespiratory fitness (CRF), measured as peak oxygen uptake (VO₂peak), and cardiovascular disease (CVD) risk, measured by arterial stiffness, in patients with ankylosing spondylitis (AS).Methods.VO₂peak was assessed by a maximal walking test on a treadmill. Arterial stiffness was measured noninvasively (Sphygmocor apparatus). Cross-sectional associations between VO₂peak and arterial stiffness were analyzed using backward multivariable linear regression.Results.Among 118 participating patients, there were significant inverse associations between VO₂peak and arterial stiffness, independent of traditional CVD risk factors and measures of disease activity.Conclusion.Reduced CRF may be related to increased risk of CVD in AS.