BACKGROUND: The presence of antiphospholipid antibodies (aPL) has been suggested as a potential cause of moyamoya angiopathy (MMA), but this remains uncertain. In this case-control study, we aimed to compare the prevalence of circulating aPL in patients with MMA and in non-MMA cerebrovascular controls. METHODS: For comparison, we included 95 patients with MMA from the French National Referral Centre for this condition and 182 age- and sex-matched non-MMA controls with a different cerebrovascular disease, all younger than 55 years. Anticardiolipin antibodies, anti-β2-glycoprotein I antibodies, and lupus anticoagulant were assessed using the guidelines of the International Society on Thrombosis and Haemostasis. RESULTS: aPL prevalence was 22% in patients with MMA and 25% in controls ( P =0.74) with no differences in aPL subtypes between the 2 groups. The prevalence of transient ischemic attacks, ischemic stroke, and hemorrhagic stroke did not differ between patients with aPL-positive and aPL-negative MMA. CONCLUSIONS: The prevalence of aPL in patients with MMA is comparable to that in non-MMA controls. The present results do not support any causal relationship between aPL and MMA.