BACKGROUND : Antegrade cerebral perfusion (ACP) is an essential adjunct for prolonged hypothermic circulatory arrest (HCA) during aortic arch surgery. However, it has yet to be established whether ACP should be delivered unilaterally or bilaterally. The aim of the present meta-analysis is to investigate outcomes of unilateral ACP (uACP) compared to bilateral ACP (bACP) in comparative studies. METHODS : Electronic searches were performed using four databases from their inception to February 2017. Relevant comparative studies with adult patients who underwent aortic arch surgery using unilateral or bilateral ACP were included. Data was extracted by two independent researchers and analysed according to predefined endpoints using a random-effects model. Meta-regression was used to identify predictors of primary outcomes. RESULTS : Nine comparative studies were identified, comprising 967 uACP patients and 879 bACP patients. No significant differences in age, sex, or proportion of total arch replacements were identified. The uACP cohort had a greater proportion of acute dissections (86% vs 75%, p = 0.04). Hypothermic circulatory arrest and cerebral perfusion times were similar between both groups. No significant differences were seen between unilateral and bilateral groups in terms of mortality (odds ratio [OR] 0.97; 95% confidence interval [CI] 0.64-1.48; p = 0.90; I2 = 0%), permanent neurological deficit (PND) (OR 1.04; 95% CI 0.74-1.45; p = 0.85; I2 = 0%), temporary neurological deficit (p = 0.74), acute kidney injury (p = 0.36) or reoperation for bleeding (p = 0.65). No factors affecting mortality or PND were identified on meta-regression. CONCLUSIONS : For patients undergoing aortic arch surgery, the available evidence supports either uACP or bACP as an adjunct to HCA. However, there is insufficient comparative evidence available to determine the benefit of either modalities in patients with longer durations of circulatory arrest.