Background: Endovascular therapy (ET) has emerged as a highly effective treatment for acute large vessel occlusion stroke (LVOS). Tools that facilitate optimal patient selection of patients for ET are needed in order to maximize therapeutic benefit in a cost-effective manner. Several pre-intervention prognostic scores for prediction of outcomes in LVOS patients and patient selection for ET have been developed and validated, but their clinical use has been limited. Here, we review existing pre-intervention prognostic scores, compare their prognostic accuracies and levels of validation and identify gaps in current knowledge. Summary: We have reviewed published literature pertinent to development, validation, and implementation of pre-intervention prognostic scores for LVOS. Using receiver operating characteristic curve analysis, the prognostic accuracies of validated pre-interventional scores (Pittsburgh Response to Endovascular therapy [PRE], Totaled Health Risks in Vascular Events [THRIVE], Houston Intra-Arterial Therapy-2 (HIAT-2), Stroke Prognostication using Age and NIHSS [SPAN-100]) were compared in published work. Pre-intervention scores predicted functional out comes at 3 months with moderate prognostic accuracies (area under the receiver operator characteristic curve range 0.68–0.73). Using successful reperfusion (mTICI 2B/3) as the therapeutic objective of ET and 3-month modified Rankin Score 0–2 as good clinical outcome, patients most likely to clinically benefit from endovascular reperfusion can be identified using the PRE and HIAT-2 scores. Scores that incorporate collateral imaging or perfusion-based estimation of core and penumbra have not been published. Existing scores are predominantly limited to anterior circulation LVOS, and implementation studies of pre-interventional scores are lacking. Key Messages: Pre-intervention prognostic scores can serve as useful adjuncts for patient selection in ET for acute LVOS. Pre-intervention scores including HIAT-2, THRIVE, SPAN-100, and PRE have comparable moderate prognostic accuracies for good 3-month outcomes and can identify patients who derive maximal benefit from successful reperfusion. Improvements in prognostic accuracy may be achieved by incorporating variables such as collateral status and perfusion imaging data. Implementation and impact studies using pre-intervention scores are needed to guide clinical application.