OBJECTIVE The vascular lumen of an acutely occluded internal carotid artery (ICA) generally contains numerous thrombi. Therefore, carotid angiography on the affected side during revascularization therapy of acute ICA occlusion has a potential risk of causing distal embolization. In this study the authors propose the use of contralateral carotid angiography. METHODS Six patients with acute ICA occlusion underwent revascularization therapy using a stent retriever or Penumbra system. Revascularization therapy was performed with placement of a 9-Fr balloon-guiding catheter (BGC) in the affected ICA and a 4-Fr diagnostic catheter in the contralateral ICA. During the procedure, the 9-Fr BGC was kept inflated, and all control angiography was performed from the 4-Fr diagnostic catheter. After thrombectomy, contralateral carotid angiography combined with manual aspiration from the 9-Fr BGC was performed to assess the presence or absence of residual thrombi in the affected ICA. The 9-Fr BGC was deflated only after the complete absence of residual thrombi in the affected ICA was confirmed. RESULTS The time required for introducing the 4-Fr diagnostic catheter into the contralateral ICA was within a few minutes in all patients. Residual thrombi in the affected ICA were found in 3 of 6 patients. The residual thrombi in these 3 patients were completely removed; thus, distal embolization was prevented. CONCLUSIONS Contralateral carotid angiography is useful for avoiding distal embolization during revascularization therapy of acute ICA occlusion. Further studies involving a larger number of patients are warranted to verify the clinical efficacy of this contralateral carotid angiography.