Gone are the days when physicians could hang their shingles just once and expect to practice in one geographical location their entire careers. Most physicians in the US now expect to relocate for professional reasons, to transfer from place to place within corporation-run health care, or to have other reasons for seeking licenses in more than one state, such as participating in tele- medicine and e-medicine. This guide, which covers osteopathic as well as allopathic physicians, gives states’ licensing requirements, including relevant examinations and fees, requirements for re- registration and CME requirements, endorsement policies for physicians holding an initial license, information on foreign medical graduates, continuing education, national boards, and licensing in the US Air Force, Army and Navy. It includes a list of references and useful web sites.