Aortic stiffness and chronic kidney disease are closely linked by shared risk factors and associated increased cardiovascular mortality. At lower levels of renal function, aortic stiffness is independently associated with glomerular filtration rate. However, the longitudinal impact of aortic stiffness on renal function has not been reported previously. A cohort of 133 patients with chronic kidney disease stages 3 and 4 (estimated glomerular filtration rate: 15 to 59 mL/min per 1.73 m(2)) underwent prospective measurement of arterial stiffness parameters and monitoring of renal function. Aortic pulse wave velocity measurement was performed in 120 patients. The mean age was 69+/-12 years (mean+/-SD; 103 men, 30 women, and 23.3% diabetic). Mean systolic blood pressure was 155+/-21 mm Hg, and mean diastolic blood pressure was 83+/-11 mm Hg. The mean Modification of Diet in Renal Disease estimated glomerular filtration rate was 32+/-11 mL/min per 1.73 m(2). Change in renal function was measured using reciprocal creatinine plots and the dichotomous combined end point of > or = 25% decline in renal function or start of renal replacement therapy. After stepwise multivariate analysis, aortic pulse wave velocity was independently associated with gradient of reciprocal creatinine plot (r=0.46; P=0.014). In multivariate analysis of the end point of > or = 25% decline in renal function or start of renal replacement therapy, independent predictors were aortic pulse wave velocity (r=0.48; P=0.002), systolic blood pressure (r=0.17; P=0.039), and urine protein:creatinine ratio (r=0.20; P=0.021). We, therefore, conclude that aortic stiffening is independently associated with rate of change in renal function in patients with chronic kidney disease stages 3 and 4.