Background and Purpose- If anterior circulation large vessel occlusion acute ischemic stroke patients presenting with ASPECTS 0-5 (Alberta Stroke Program Early CT Score) should be treated with mechanical thrombectomy remains unclear. Purpose of this study was to report on the outcome of patients with ASPECTS 0-5 treated with mechanical thrombectomy and to provide data regarding the effect of successful reperfusion on clinical outcomes and safety measures in these patients. Methods- Multicenter, pooled analysis of 7 institutional prospective registries: Bernese-European Registry for Ischemic Stroke Patients Treated Outside Current Guidelines With Neurothrombectomy Devices Using the SOLITAIRE FR With the Intention for Thrombectomy (Clinical Trial Registration-URL: https://www.clinicaltrials.gov . Unique identifier: NCT03496064). Primary outcome was defined as modified Rankin Scale 0-3 at day 90 (favorable outcome). Secondary outcomes included rates of day 90 modified Rankin Scale 0-2 (functional independence), day 90 mortality and occurrence of symptomatic intracerebral hemorrhage. Multivariable logistic regression analyses were performed to assess the association of successful reperfusion with clinical outcomes. Outputs are displayed as adjusted Odds Ratios (aOR) and 95% CI. Results- Two hundred thirty-seven of 2046 patients included in this registry presented with anterior circulation large vessel occlusion and ASPECTS 0-5. In this subgroup, the overall rates of favorable outcome and mortality at day 90 were 40.1% and 40.9%. Achieving successful reperfusion was independently associated with favorable outcome (aOR, 5.534; 95% CI, 2.363-12.961), functional independence (aOR, 5.583; 95% CI, 1.964-15.873), reduced mortality (aOR, 0.180; 95% CI, 0.083-0.390), and lower rates of symptomatic intracerebral hemorrhage (aOR, 0.235; 95% CI, 0.062-0.887). The mortality-reducing effect remained in patients with ASPECTS 0-4 (aOR, 0.167; 95% CI, 0.056-0.499). Sensitivity analyses did not change the primary results. Conclusions- In patients presenting with ASPECTS 0-5, who were treated with mechanical thrombectomy, successful reperfusion was beneficial without increasing the risk of symptomatic intracerebral hemorrhage. Although the results do not allow for general treatment recommendations, formal testing of mechanical thrombectomy versus best medical treatment in these patients in a randomized controlled trial is warranted.