Aims: The effect of allopurinol on flow-mediated dilation (FMD), an index of endothelial function in humans, remains inconsistent. We performed a meta-analysis to determine whether allopurinol therapy could improve FMD. Methods: Human intervention studies were identified by systematic searches of Medline, Embase, Cochrane's library, and references of related reviews and studies. A random-effect model was applied to estimate the pooled results. Results: Ten randomized controlled trials with 594 subjects at risk of cardiovascular risks were included. Results of the meta-analysis indicated that allopurinol therapy significantly improved FMD in these subjects as compared with control groups (WMD=1.67%, 95% CI: 0.83% similar to 2.50%, P<.001; I-2=86%), with no evidence of significant heterogeneity if only double-blinded studies were included (WMD=1.36%, 95% CI: 0.89% similar to 1.83%, P<. 001; I-2=21%). Results of metaregression and subgroup analyses suggested that the benefit of allopurinol to FMD seemed to be not related to its uric acid (UA)-lowering action. Moreover, allopurinol therapy may be associated with more remarkable improvement of FMD in subjects with lower serum UA (<7 mg/dL: WMD=2.62%, 95% CI: 1.10% similar to 4.14%), compared to those with higher UA (>= 7 mg/dL: WMD=0.87%, 95% CI: 0.37% similar to 1.38%; P for subgroup difference =.03). Conclusions: Allopurinol therapy is associated with significantly improved endothelial function in subjects at risk of CVD risks, and the beneficial effects of allopurinol seemed to be more remarkable in patients with normal UA at baseline.