Stereotactic body radiotherapy (SBRT) has been suggested as a promising therapeutic alternative in cases of failed catheter ablation for recurrent ventricular tachycardias (VTs) in patients with structural heart disease. This case series is the first postmortem immunohistochemical analysis of morphologic changes in the myocardium early and late after SBRT. The present findings are in line with experimental observations on apoptosis followed by fibrosis. This may explain why the effect of SBRT on VT is not predominantly immediate. Together with observation of early recurrences after SBRT for VT, these data suggest that this strategy may have rather delayed antiarrhythmic effects. (J Am Coll Cardiol EP 2021;7:1487-1492) (c) 2021 by the American College of Cardiology Foundation.