Background: We examined which pathophysiological abnormalities of vascular function might be closely associated with abnormal baroreflex regulation in subjects with hypertension. Methods and Results: In the cross-sectional assessment, 280 subjects with hypertension were enrolled for measurement of brachial-ankle pulse wave velocity (baPWV), radial augmentation index (rAI), flow-mediated vasodilatation (FMD) of the brachial artery and baroreceptor sensitivity (BRS). These parameters were measured again as prospective assessment in some of these subjects. In the cross-sectional assessment, after adjustment for confounding variables including anti-hypertensive medication, the baPWV, but not the rAI or FMD, was found to have a significant independent relationship with BRS (standardization coefficient, –0.149, P<0.043). In the subjects who were newly started on anti-hypertensive medication (n=40), regression of baPWV before and 1 year after the start of medication was significantly associated with change in BRS during the same period. In subjects already on anti-hypertensive medication (n=92) also, the evolutional change of baPWV over a follow-up period >1.5 years was significantly associated with change in BRS during the same period. Conclusions: Increased stiffness of the large- to middle-sized arteries, rather than abnormal central hemodynamics or endothelial dysfunction, appears to contribute to abnormal baroreflex regulation in patients with hypertension.  (Circ J 2014; 78: 1414–1419)