Microbial biofilms constitute a major reason for infections to occur and persist at various sites in the human body, especially in association with medical devices. The organisms invariably form these biofilms on surfaces which have host proteins and other substances coating them. Once adherent, the bacteria multiply and anchor themselves in quite intricate structures which appear to allow for communication and information transfer between organisms. For the treating physician, many antibiotics are unable to eradicate dense biofilms, and therefore much work is required to devise ways to prevent their occurrence and clear them from the host. Copyright (C) 1999 Elsevier Science B.V.