The importance of xanthine oxidase and its products is being increasingly recognized in cardiovascular medicine. Patients who have had a stroke are at high risk of future cardiovascular events and this risk is higher in those with high urate levels. The aim of this pilot study was to see if inhibiting xanthine oxidase altered arterial wave reflection, determined from the augmentation index (AIx). In a double-blind study, 30 patients with high urate (≥0.38 mmol/L) were randomized to 300 mg allopurinol or placebo for 8 weeks. AIx measurements were made before and after treatment using the validated SphygmoCor pulse waveform analysis system. For patients treated with allopurinol, there was a reduction in AIx from 26.08 ± 3.31% to 20.15 ± 2.23% compared with an increase in the placebo group from 23.57 ± 3.13% to 27.64 ± 3.44% (P= 0.031, ANOVA). The vascular benefits of allopurinol are rapidly emerging. We have demonstrated that allopurinol has beneficial effects on AIx, a validated measure of vascular function. A further larger study is warranted to look at whether a therapeutic intervention with allopurinol will impact positively on mortality and morbidity in stroke survivors.