On November 23, 2006, former Russian military intelligence officer Alexander Litvinenko died in a London hospital. Authorities determined he was deliberately poisoned with the radionuclide Polonium-210 (210Po). Police subsequently discovered that those involved in this crime had--apparently inadvertently--spread 210Po over many locations in London. The United Kingdom Health Protection Agency (HPA) contacted many persons who might have been exposed to 210Po and provided voluntary urine testing. Some of those identified as potentially exposed were U.S. citizens, whom the HPA requested that the Centers for Disease Control and Prevention (CDC) assist in contacting. CDC also provided health care professionals and state and local public health officials with guidance as to how they might respond should a Litvinenko-like incident occur in the U.S. This guidance has resulted in the identification of a number of lessons that can be useful to public health and medical authorities in planning for radiological incidents. Eight such lessons are discussed in this article.