Coronary stenting is now used in most coronary interventions and reduces the restenosis rate to 20% or less. However, repeat in-stent restenosis occurs in 40%–60% of these patients. Radiation therapy, guided by intravascular ultrasound, can further reduce the incidence of repeat in-stent restenosis, and clinical trials have shown that all patient subgroups benefit from it. The mechanism appears to be reduction in neointimal hyperplasia. Studies are now evaluating use of medication with stents and radiotherapy, implantation of radiation-eluting stents, longer radiation sources to adequately cover lesions, and catheter balloons inflated with radioisotope solution. Intravascular radiation may soon be the standard of treatment for patients with in-stent restenosis and has the potential to reduce the recurrence rate to below 10%.