Antibody-based therapies are effective against a wide variety of pathogens. Historically, antibody-based therapies were largely abandoned with the advent of antimicrobial chemotherapy, due to the toxicity associated with the administration of heterologous immune sera. As a class, antibody-based therapies have significant advantages and disadvantages relative to conventional antimicrobial chemotherapy. Advantages include versatility, specificity, and antimicrobial activities not available in antibiotic drugs, such as toxin and viral neutralisation, opsonisation, complement activation and the enhancement of host immune function. Disadvantages include expense, the necessity for early and accurate diagnosis prior to use, and the complex logistics necessary for therapeutic use. Advances in antibody technology have minimised some of the disadvantages associated with antibody therapy. In recent years, the therapy of infectious diseases has been complicated by the emergence of new pathogens, the spread of antibiotic-resistant strains and the relative inefficacy of antimicrobial chemotherapy in immunocompromised hosts. This has led to renewed interest in the utilisation of antibody-based therapies as anti-infectives. Many opportunities for developing antibody-based drugs now exist in areas where the available antimicrobial therapies are inadequate.