Vascular endothelial dysfunction and arterial stiffness are common in chronic kidney disease (CKD) and independently predict cardiovascular disease (CVD). Elevated serum phosphorus, even within the normal range, associates with CVD and mortality in CKD. Excess phosphorus may increase oxidative stress leading to vascular dysfunction. Randomized double-blind trial in which we compared lanthanum carbonate, a non-calcium phosphate binder, with placebo on vascular function and endothelial and circulating measures of oxidative stress and inflammation in 54 participants with CKD 3b-4 and normal phosphorus levels. The primary endpoints were change in brachial artery flow-mediated dilation (FMDBA) and carotid-to-femoral pulse-wave velocity (cfPWV) at 12 weeks. Mechanistic endpoints were changes from baseline in FMDBA after ascorbic acid infusion and circulating and endothelial markers of oxidative stress and inflammation. Age was 65±8 years and eGFR 38±14 mL/min/1.73m2. At 12 weeks serum phosphorus did not change with lanthanum (3.44±0.47 mg/dL vs. 3.44±0.52 mg/dL; p=0.94) but tended to increase with placebo (3.42±0.80 mg/dL vs. 3.74±1.26 mg/dL; p=0.09). FMDBA and cfPWV did not change from baseline in either group. FMDBA lanthanum 3.13%±2.87% to 2.73%±2.48% vs. placebo 3.74%±2.86% to 3.09%±2.49%; p=0.67. cfPWV lanthanum 1214±394 cm/sec to 1216±322 cm/sec vs. placebo 993±289 cm/sec to 977±254 cm/sec; p=0.77. Ascorbic acid infusion to inhibit oxidative stress did not differentially affect FMDBA. Circulating and endothelial markers of oxidative stress and inflammation did not differ between groups. Lanthanum carbonate did not discernibly affect vascular endothelial function, arterial stiffness, or markers of endothelial oxidative stress among participants with CKD 3b-4 and normophosphatemia.