There is growing public awareness of the threat of bioterrorism, and concern among medical and public health officials as well. Substantial national preparedness measures were taken in June 1995 with Presidential Directive 39 (PDD-39), which defined the responsibilities and coordination among the Federal agencies involved. Of the weapons of mass destruction (WMD), the biological ones are the most greatly feared, but the country is least well prepared to deal with them. An aerosol cloud of a biological agent is invisible, odorless, and tasteless. First responders would be emergency room physicians and nurses, family physicians, infectious disease specialists, infection control practitioners, epidemiologists, hospital and public health administrators, and laboratory experts. Bioweapons programs began to receive substantial attention during World War II. Any one of thousands of biological agents that are capable of causing human infection could be considered a potential biological weapon. Smallpox and anthrax pose by far the greatest threats. Smallpox poses an unusually serious threat because virtually everyone is now susceptible since vaccination stopped 20 or more years ago. A scenario for an inhalation anthrax epidemic is of no less concern, with infected individuals appearing in emergency rooms and doctors’ offices within 2 to 3 days after exposure. The symptoms include fever, cough, and headache. Individuals who are exposed to an aerosol may abruptly develop illness up to 8 weeks after the initial exposure. The need to discuss bioterrorism in national forums remains. The most effective step is to strengthen the public health and infectious disease infrastructure. There is a need to train primary care doctors in early recognition of the most important disease threats and to intensify the training of emergency room physicians and nurses. Other critical needs are improved vaccines for both smallpox and anthrax in large supply. There is also a need to pursue measures that will prevent acts of terrorism. 24 references