The term quorum sensing (QS) is used to describe communication between bacterial cells, whereby a coordinated population response is controlled by diffusible signal molecules produced by individuals.Studies on QS-mediated signalling processes in bacteria have revealed the existence of intricate regulatory networks to enable bacterial populations to fine tune their responses to environmental changes and increase their chances of survival, using complex signalling pathways.A population of bacteria invading a host may benefit from the coordinated release of virulence determinants and in vitro studies have shown that QS regulates virulence factor production in many species of bacteria.However, the role of QS in vivo is less well understood, but has been demonstrated to be important in several pathogenic organisms.There is a growing interest in blocking bacterial cell-cell communication as a means to control infections. This review discusses QS from a pathogenic perspective and discusses the potential of QS as an anti-pathogenic target.