Cardiovascular brachytherapy, the use of high intensity radiation to inhibit the growth of neointimal tissue after coronary revascularization by either balloon angioplasty or other methods is being tested in a number of clinical trials to assess the efficacy of the treatment. This new use of radiation to aleviate the suffering of individuals with coronary artery disease has excited many interventionalists and has caused others to view the new technique with skepticism. There are a number of operational and safety concerns to face in incorporating this treatment modality into the cardiac catheterization laboratory. Delivering the radiation dose to the patient with a minimum of radiation exposure to both patient and operating personnel requires close attention to the physical characteristics of the radiation source as well as the administrative and regulatory requirements imposed on the facility by federal and state regulators. The insertion of the source into the proper artery and location is the task of the cardiologist in collaboration with the radiation oncologist. The determination of the appropriate radiation dose is the responsibility of the medical physicist. The safe handling of the radioisotope source is the responsibility of the radiation safety specialist. State and federal regulations dictate minimum requirements of safety in the handling of radioactive sources used in cardiovascular brachytherapy. These requirements involve close monitoring of the patient and operating personnel to insure that radiation exposures are minimized. They involve the restricted access of nonessential personnel to the cath lab during the treatment. The entrances to the cath lab must be monitored to prevent unauthorized entry. Operating personnel must be closely monitored to maintain radiation exposures as low as reasonably achievable (ALARA). The patient must be monitored to insure that the source is implanted for the prescribed time and the patient's exposure is also ALARA consistent with the medical benefit expected. Public corridors must be monitored to prevent public exposures to the radiation emanating from the patient. The radiation exposure field around the patient during a typical gamma treatment presents what the regulators define as a high radiation area. This means that the exposure levels are in excess of 100 milli-rem (mrem) per hour at 30 cm from the patient. In fact, the exposure levels around the patient for a typical treatment are in the roentgens per hour range. The use of beta particle emitting radionuclides (Sr90/Y90 and P32) presents a much lower safety problem. But the use of radioactive materials in the cath lab still presents new safety concerns such as training, monitoring, record keeping, and public relations among the cath lab technologists.