Pneumonic plague, a disease caused by the bacterium Yersinia pestis, is a rare disease in the United States and carries a high mortality. Health care professionals in the United States are not familiar with the clinical presentation and diagnosis of plague pneumonia. The wide prevalence of the bacterium in different parts of the world, its high virulence, and its ability to spread by aerosolization makes it a potential agent of biological warfare in the hands of terrorists. This review focuses on the prevalence, pathogenesis immunity, clinical manifestations, diagnosis, treatment, and prevention of plague pneumonia, with particular emphasis on the plague bacillus as an agent of biological warfare. Based on available information, we discuss measures that need to be undertaken by health care personnel, public health personnel, and epidemiologists in the event of such an attack.