From the anthrax attacks, the U.S. Postal Service (USPS) and other agencies have learned that the risk of anthrax exposure through the mail is higher than they had assumed, since the number of anthrax spores that can cause illness and possibly death is far fewer than previously understood; thus, they must respond more cautiously to this higher risk. USPS officials also learned they must communicate clearly and accurately with postal employees and the public, must respond more quickly to such threats to safety, and must manage their response better. The public health response to the anthrax incidents showed that local, State, and Federal agencies already have cooperative procedures in place or under way, but they must reinforce or expand these measures. The U.S. Department of Health and Human Services coordinated the public health response to the anthrax attack, primarily through the Centers for Disease Control (CDC), but the CDC had no experience in responding simultaneously to multiple disease outbreaks caused by the intentional release of an infectious agent. Physicians and hospitals quickly needed information from public health officials about how to recognize anthrax exposure and treat exposed patients. Overall, the lessons learned from the anthrax letters pertain to the benefits of prior planning and experience; the importance of effective communication, both among responders and with the public; and the critical importance of a strong public health infrastructure. Of particular importance is preparation for and expanded communications and coordination network that encompasses not only relevant public agencies but also private organizations with expertise pertinent to an attack. This article describes various steps that have been taken to improve biohazard detection and decontamination by the USPS, as well as improvements by the CDC in its ability to respond to a terrorism event.