Human plague is a local or systemic flea-transmitted infection caused by Yersinia pestis. It is maintained in well established enzootic foci among wild rodents. This article discusses the clinical findings in plague, diagnosis, treatment, and prevention of plague, and management of contacts of human plague cases and of exposures to epizootic plague. Tularemia shares many features with plague but is widespread in animal and arthropod vector populations and essentially throughout the United States.