Xiangping Cheng,1,2,* Boyu Chen,3,* Xiaoyan Chen,4,* Zhi Song,2 Jie Li,2 Jiacheng Huang,4 Weilin Kong,4 Jinglun Li1 1Department of Neurology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, People’s Republic of China; 2Department of Neurology, The Gulin People’s Hospital, Luzhou, Sichuan Province, People’s Republic of China; 3Department of Cerebrovascular Diseases, Qujing No. 1 Hospital, Qujing, Yunnan, People’s Republic of China; 4Department of Neurology, Xinqiao Hospital and the Second Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jinglun Li, Department of Neurology, The Affiliated Hospital of Southwest Medical University, No. 25 Taiping Street, Jiangyang District, Luzhou City, Sichuan Province, 646000, People’s Republic of China, Email ljl031611@163.com Weilin Kong, Department of Neurology, Xinqiao Hospital and the Second Affiliated Hospital, Army Medical University (Third Military Medical University), No. 183 Xinqiao Main Street, Shapingba District, Chongqing, 400037, People’s Republic of China, Email kongweilin96@whu.edu.cnPurpose: Renal impairment (RI) is associated with unfavourable outcome after acute ischaemic stroke with anterior circulation large vessel occlusion. We assessed the association of RI with clinical outcomes in patients with acute basilar artery occlusion (ABAO), and the impact of RI on the effects of endovascular therapy (EVT) versus standard medical treatment (SMT).Patients and Methods: We used data from the BASILAR registry, an observational, prospective, nationwide study of patients with ABAO in routine clinical practice in China. Baseline estimated glomerular filtration rate (eGFR) was recorded at admission. The primary outcome was the modified Rankin Scale (mRS) score at 90 days. Secondary outcomes included favourable outcome (mRS score 0– 3), mortality, and symptomatic intracranial haemorrhage (sICH). Multivariate logistic regression was used to assess the association of RI with mortality and functional improvement at 90 days.Results: Among 829 patients enrolled, 747 patients were analysed. The median baseline eGFR was 89 mL/min/1.73m2 (IQR, 71– 100), and 350 (46.8%), 297 (39.8%), and 100 (13.4%) patients had baseline eGFR values of ≥ 90, 60– 89, and < 60 mL/min/1.73m2, respectively. RI was associated with increased mortality (adjusted odds ratio [aOR], 1.97; 95% CI, 1.15– 3.67) at 90 days and decreased survival probability (aOR 1.74; 95% CI, 1.30– 2.33) within 1 year. EVT was associated with better functional improvement (common aOR, 2.50; 95% CI, 1.43– 4.35), favourable outcome (aOR 5.42; 95% CI, 1.92– 15.29) and lower mortality (aOR 0.47; 95% CI, 0.25– 0.88) in ABAO patients with eGFR ≥ 90 mL/min/1.73m2. However, RI was not modified the relationship of EVT with functional improvement (common aOR, 3.03; 95% CI, 0.81– 11.11), favourable outcome (aOR 2.10; 95% CI, 0.45– 9.79), and mortality (aOR 0.56; 95% CI, 0.15– 2.06) by eGFR categories.Conclusion: RI is associated with reduced efficacy of EVT and worse functional outcome and higher mortality at 3 months and lower survival probability at 1 year in patients with ABAO.Keywords: ischemia stroke, basilar artery occlusion, renal impairment, endovascular therapy, glomerular filtration rate