Yersinia pestis, the aetiological agent of plague, has in the past caused social devastation on a scale unmatched by other infectious diseases. There is still a public health problem from plague, with at least 2000 cases reported annually. Most of these cases are of the bubonic form. Occasionally bubonic plague develops into pneumonic plague, and this form of the disease can spread rapidly between susceptible individuals. The recent outbreak of plague in India highlighted the potential for plague to explosively re-appear, and modern mass transport systems mean that there is the potential for the rapid spread of disease. Against this background, there is a need to ensure that vaccines and antibiotics are available to prevent and treat the disease. Progress has been made in devising a sub-unit vaccine, effective against bubonic and pneumonic plague. Antibiotics must be given in the early stages of disease to effect a cure.