In 2005, the Health Physics Society celebrates its 50th anniversary. During its half century of existence, the Society has evolved from a small group of operationally oriented radiation protection scientists into an organization of several thousand with a recognized and respected peer reviewed journal. The bold decision to form an organization devoted to radiation safety in the United States spurred the formation of such societies in other countries and led to the formation of an international confederation of national societies, which has facilitated scientific communication and exchange worldwide. It also led to the formation of a separate body for the certification of health physicists, which in turn has grown into an academy with more than 1,000 members, and was instrumental in providing basic information establishing the need for a registry of radiation protection technologists.