Background The Totaled Health Risks in Vascular Events (THRIVE) score strongly predicts clinical outcome, mortality, and risk of thrombolytic haemorrhage in ischemic stroke patients, and performs similarly well in patients receiving intravenous tissue plasminogen activator, endovascular stroke treatment, or no acute treatment. It is not known if the THRIVE score predicts outcomes with the Solitaire endovascular stroke treatment device. Aims To validate the relationship between the THRIVE score and outcomes after treatment with the Solitaire endovascular stroke treatment device. Methods The study conducted a retrospective analysis of the prospective SWIFT and STAR trials to examine the relationship between THRIVE and outcomes after treatment with the Solitaire device. We examined the relationship between THRIVE and clinical outcomes (good outcome or death at 90 days) among patients in SWIFT and STAR. Receiver-operator characteristics curve analysis was used to compare THRIVE score performance with other stroke prediction scores. Multivariable modeling was used to confirm the independence of the THRIVE score from procedure-specific predictors (successful recanalization or device used) and other predictors of functional outcome. Results The THRIVE score strongly predicts good outcome and death among patients treated with the Solitaire device in SWIFT and STAR (Mantel-Haenszel chi-square test for trend P < 0·001 for good outcome, P = 0·01 for death). In receiver-operator characteristics (ROC) curve comparisons, totaled health risks in vascular events score is superior to Stroke Prognostication using Age and NIH Stroke Scale score-100 ( P < 0·001) and performed similarly to Houston Intra-Arterial Therapy score (HIAT) ( P = 0·98) and HIAT-2 ( P = 0·54). In multivariable models, THRIVE's prediction of good outcome is not altered after controlling for recanalization or after controlling for device used. The THRIVE score remains a strong independent predictor after controlling for the above predictors together with time to procedure, rate of symptomatic haemorrhage, and use of general anesthesia. Of note, use of general anesthesia was not an independent predictor of outcome in SWIFT + STAR after controlling for totaled health risks in vascular events and other factors. Conclusions The THRIVE score strongly predicts clinical outcome and mortality in patients treated with the Solitaire device in the SWIFT and STAR trials. The lack of interaction between THRIVE and procedure-specific elements such as vessel recanalization or device choice makes the THRIVE score a reasonable candidate for use as a patient selection criterion in stroke clinical trials.