Abstract Background and Purpose Data regarding the safety and efficacy of intravenous tPA (tissue-type plasminogen activator) in childhood acute arterial ischemic stroke are inadequate. The TIPS trial (Thrombolysis in Pediatric Stroke; National Institutes of Health grant R01NS065848)—a prospective safety and dose-finding trial of intravenous tPA in acute childhood stroke—was closed for lack of accrual. TIPS sites have subsequently treated children with acute stroke in accordance with established institutional protocols supporting data collection on outcomes. Methods Data on children treated with intravenous tPA for neuroimaging-confirmed arterial ischemic stroke were collected retrospectively from 16 former TIPS sites to establish preliminary safety data. Participating sites were required to report all children who were treated with intravenous tPA to minimize reporting bias. Symptomatic intracranial hemorrhage (SICH) was defined as ECASS (European Cooperative Acute Stroke Study) II parenchymal hematoma type 2 or any intracranial hemorrhage associated with neurological deterioration within 36 after following tPA administration. A Bayesian model for risk of SICH following intravenous tPA was fit using a prior distribution based on the risk level in young adults (1.7%); to test for robustness, the model was also fit with uninformative and conservative priors. Results Twenty-six children (age range, 1.1–17 years; median, 14 years; 12 boys) with stroke and a median pediatric National Institutes of Health Stroke Scale score of 14 were treated with intravenous tPA within 2 to 4.5 hours (median, 3.0 hours) after stroke onset. No patient had SICH. Two children developed epistaxis. Conclusions The estimated risk of SICH after tPA in children is 2.1% (95% highest posterior density interval, 0.0%–6.7%; mode, 0.9%). Regardless of prior assumption, there is at least a 98% chance that the risk is <15% and at least a 93% chance that the risk is <10%. These results suggest that the overall risk of SICH after intravenous tPA in children with acute arterial ischemic stroke, when given within 4.5 hours after symptom onset, is low. Footnotes Presented in part at the International Stroke Conference, Honolulu, HI, February 6–8, 2019. The online-only Data Supplement is available with this article at https://www.ahajournals.org/doi/suppl/10.1161/STROKEAHA.119.027225 Correspondence to Catherine Amlie-Lefond, MD, Seattle Children’s Hospital, 4800 Sand Point Way NE, Seattle, WA 98105. Email firstname.lastname@example.org To view this full article click here.