<h3>Purpose/Objective(s)</h3> Ventricular tachycardia (VT) is characterized by electrical re-entry within patches of heterogeneous myocardial fibrosis leading to sustained consecutive ventricular beats at a rate > 100 per minute. Implantable cardioverter-defibrillators (ICD) are the main intervention for reducing mortality, however, they are exclusively a symptom-control therapy. Catheter ablation is the standard of care adjunctive therapy for patients who are refractory to medical therapy. Recently, a treatment approach with a stereotactic body radiation therapy (SBRT) to arrhythmogenic scar regions has been described. Initial results, using a single 25 Gy fraction, suggest this technique may improve morbidity for patient's refractory to standard of care therapy. The optimal dose for this therapy remains unclear and major adverse events with 25 Gy have been reported. This clinical trial hypothesizes that refractory VT treated with SBRT in a single fraction of 20 Gy is non-inferior to 25 Gy. <h3>Materials/Methods</h3> Inclusion criteria are age > 18 years, cardiomyopathy, recurrent episodes of monomorphic VT failing standard treatment with at least 1 antiarrhythmic drug and previous electrophysiologic ablation. Exclusion criteria are participants with previous thoracic radiation, connective tissue disease, interstitial pulmonary fibrosis, and pregnancy. Participants with contraindications to electrophysiology studies may be eligible for the study, provided the arrhythmic substrate can be defined through other non-invasive methods. We anticipate an incidence rate of approximately 5 VT events per person-year in participants treated with 25 Gy as a historical comparator based on a previous phase I/II trial. Based on a Poisson distribution, and using a non-inferiority margin of 8.5 events per-year (incident rate ratio of 1.70), recruiting 9 participants will provide 80% power when using a one-sided type I error, set at 0.05. Non-inferiority of 20 Gy relative to 25 Gy will be determined if the upper bound of the one-sided 95% confidence interval for the incidence rate ratio is below the pre-specified non-inferiority margin (incidence rate ratio=1.70). The primary efficacy endpoint is the reduction in arrhythmia burden measured by the total number of VT events and ICD treatments for VT comparing the 6 and 12-month periods after a single fraction of 20 Gy SBRT with a single fraction of 25 Gy in the published literature. Our primary safety endpoint is defined as the rate of severe treatment-related adverse events at ≤ 90 days as defined by the CTCAE v5.0. Secondary endpoints include overall survival, late adverse events, antiarrhythmic drug use, and quality of life. <h3>Results</h3> The Research Ethics Board at the institution has approved this research study and will provide ongoing ethical oversight. <h3>Conclusion</h3> This study is currently recruiting participants. This trial is registered at ClinicalTrials.gov, NCT05258422.