The only gamma emitter used in clinical trials for in-stent restenosis is 192Iridium (192Ir). The efficacy of intracoronary gamma radiation therapy in reducing clinical and angiographic restenosis in patients with in-stent restenosis has been established. This review is intended to give an overview of the clinical trials utilizing gamma vascular brachytherapy in patients with in-stent restenosis and give insight into the future of intracoronary radiation therapy.