Antibody-based therapies are currently undergoing a renaissance. After being developed and then largely abandoned in the twentieth century, many antibody preparations are now in clinical use. However, most of the reagents that are available target non-infectious diseases. Interest in using antibodies to treat infectious diseases is now being fuelled by the wide dissemination of drug-resistant microorganisms, the emergence of new microorganisms, the relative inefficacy of antimicrobial drugs in immunocompromised hosts and the fact that antibody-based therapies are the only means to provide immediate immunity against biological weapons. Given the need for new antimicrobial therapies and many recent technological advances in the field of immunoglobulin research, there is considerable optimism regarding renewed applications of antibody-based therapy for the prevention and treatment of infectious diseases.