Bacterial pathogens have been identified as agents that have been, or could be, used as weapons of biological warfare and/or biological terrorism. These agents are relatively easily obtained, prepared, and dispersed, either as weapons of mass destruction or for more limited terrorist attacks. Although phylogenetically diverse, these agents all have the potential for aerosol dissemination. Physicians in the United States and most of the developed world have never encountered most of these agents and the diseases they produce. Public health programs must be prepared, and individual primary care providers must be able to recognize, diagnose, treat, and prevent infection with these agents.