In response to an outbreak of a plague-like disease in India, the Public Health Laboratory Service (PHLS) in the UK distributed advice on the isolation and identification of Yersinia pestis. Some of the procedures outlined were evaluated using a number of isolates of Y. pestis, complemented with in-house techniques detecting virulence genes or their products. These laboratory investigations are limited in that they are either only indicative or they take too long (48 hours or more), and thus represent a serious delay to the patient. Successful patient management must be based on a case history, and therapy should be started immediately. Laboratory diagnosis will subsequently rule out most pathogens which cause similar infections, yet will still require confirmation by a reference laboratory.