Vascular brachytherapy has been the subject of an extensive ongoing investigation into the safety and efficacy of this technique for preventing restenosis. Preclinical studies have demonstrated reduction of the neointimal proliferation and the late vascular constriction with radiation therapy. However, radiation is also known to delay the healing process and may contribute to a new phenomenon of late thrombosis. We report on two cases of patients with in-stent restenosis who underwent intervention followed by intracoronary vascular radiation therapy (utilizing beta and gamma radiation) and presented with acute onset of unstable angina. Angiographic study demonstrated late thrombosis, which were treated successfully with the Angiojet thrombectomy device.