Intracoronary brachytherapy has been established in Europe and the US as an evidence-based treatment of in-stent restenoses. The objective of the IST Registry is to register all patients treated in Germany with intracoronary radiation and to observe the clinical outcome for a duration of 5 years. The required set of data for each patient is kept to a minimum to encourage participation. All data are entered online. In the internet, each participating site can, at any time, check their most important parameters and compare them with those of other sites. Presently, the Novoste System is used in 58 catheter labs and the Guidant System in 16, while several sites use both. The requirements regarding radiation safety in intracoronary application of gamma radiation are very strict in Germany, so the Cordis-Gamma System is used in only one German lab. In a first analysis of 332 radiated stenoses, it was observed that late vessel occlusion could occur even after 6-month administration of clopidogrel (in addition to ASA)--without new stents being implanted within the brachytherapy session. Clopidogrel should thus be administered in addition to aspirin for at least a year. Ca. 270 patients per month receive intracoronary radiation in Germany, so the IST Registry will provide important data regarding long-term observation and a foundation for future negotiations with insurance companies potentially bearing the costs. At present, neither the physician's service nor the material costs are reimbursed. The IST Registry can furthermore be used as a comparative database regarding long-term outcome following implantation of antiproliferative-coated stents.