© American Roentgen Ray Society. OBJECTIVE. The purpose of this article is to review the training requirements for practicing nuclear radiology, the scope of licensing, how to start a new practice, and the key concepts an authorized user needs to know for responsible use of radiopharmaceuticals. CONCLUSION. Physicians responsible for the daily operations of nuclear medicine clinics often find the regulations concerning the safe handling and administration of radiopharmaceuticals daunting. Even experienced authorized users have concerns about handling many new therapeutic agents. Those studying for certifying and subspecialty examinations or for maintenance of certification for the American Board of Nuclear Medicine and the American Board of Radiology must clearly understand the overall process for becoming an authorized user.