In 200 patients with CTO randomized in the PRISON I study, we demonstrated a restenosis rate of 22% after bare metal stent implantation as compared with 33% after conventional balloon angioplasty. During the past few years, sirolimus (rapamycin), a cytostatic macrocyclic lactone with anti-inflammatory and antiproliferative properties, delivered from a polymer-encapsulated stent was shown to almost eliminate the risk of restenosis in selected groups of patients.