So far, most monoclonal antibodies have been developed for treating cancer or immunological diseases. However, the global spread of infections such as West Nile and corona viruses, and the need to address the potential threat of bioterrorism, has boosted public interest in, and government support of, counter-measures for infectious diseases. The attractive features of monoclonal antibodies, such as high specificity and effective recruitment of the immune system, would seem to make them excellent candidates as anti-infective agents. Here, we analyse trends in the development and approval of anti-infective monoclonal antibodies, and discuss factors that influence their success.