Spread of thrombus material in previously unaffected vessels is a potential hazard of mechanical thrombectomy, but it has not yet been investigated in detail, to our knowledge. Our purpose was to evaluate the frequency and relevance of these events in mTE of M1 occlusions. We retrospectively reviewed all patients treated for isolated M1 occlusion between January 2008 and July 2012. Angiographic images were analyzed to assess emboli in anterior cerebral artery branches induced by mTE and associated devices. Recanalization attempts in the ACA were reported as well as technical success and adverse events of rescue therapies. ACA infarcts on follow-up imaging served as a surrogate for clinical relevance. ACA infarcts were quantified volumetrically and assessed visually for involvement of motor or supplementary motor areas. New ACA emboli occurred in 12 of 105 (11.4%) M1 recanalization procedures and were caused by a stent-retriever in 11 intances. Attempts to recanalize the ACA were made in 6 patients and were deemed technically successful in 5 with no adverse events. We detected 6 (5.7%) new infarcts on follow-up imaging with an average volume of 26.9 cm(3). Involvement of motor or supplementary motor areas was seen in 4 (3.8%) cases. Three patients developed ACA infarcts despite successful endovascular ACA recanalization. The frequency of ACA emboli in mTE of M1 occlusions is relevant, causing ACA infarcts in 5.7% of patients; 3.8% of emboli were likely to hamper motor-function recovery. Endovascular recanalization of major ACA branches reduced the incidence of infarcts with no adverse events.