CKD is an independent risk factor for cardiovascular disease (CVD)4. Increased arterial stiffness, as measured by pulse wave velocity (PWV), is a characteristic feature of CKD5, a recognised marker of CVD risk5,6, and an independent predictor of mortality and survival in CKD6,7. To date, there have been no studies of arterial stiffness in those with pre-dialysis CKDu. Furthermore, it remains unclear whether the CVD risk associated with CKDu is the same as that of CKD of known cause. We hypothesised that CKDu patients would have increased arterial stiffness compared to matched controls but that these measures would be no different compared to matched subjects with defined aetiologies for their CKD.