['So far, relatively few studies have addressed the use of stem cells to treat patients with refractory angina. Moreover, the results of current studies were discrepant. The objective of this meta-analysis was to evaluate the efficacy and safety of this treatment on a relatively large scale.', 'Studies were identified through PubMed, CENTRAL, EMBASE, reviews, and reference lists of relevant papers. The weighted mean difference was calculated with random-effect models for net changes in exercise tolerance and angina frequency, and odds ratio (OR) with fixed-effect models for myocardial infarction (MI) and death.', 'Five randomized controlled trials, with a total of 381 patients, were included in the analysis. Compared with the controls, patients who received stem cell therapy had a significant improvement in exercise tolerance of 61.3 seconds (95% confidence interval [CI], 18.1-104.4; P = 0.005; I(2) = 58%); an obvious reduction in angina frequency of 7.3 episodes per week (95% CI, -13.4 to -1.2; P = 0.02; I(2) = 93%); and lower risk of MI, with an OR of 0.37 (95% CI, 0.14-0.95; P = 0.04; I(2) = 0%). No difference was detected for the risk of death (OR, 0.33; 95% CI, 0.08-1.39; P = 0.13; I(2) = 20%).'] Is stem cell therapy a promising tool for refractory angina : a meta-analysis of randomized controlled trials?