Ribavirin is a very broad-spectrum virustatic antiviral agent, first synthesised in 1972. It is characterised by low toxicity apart from reversible anaemia, usually mild. Its multiple mechanisms of action mean that viral resistance rarely develops. It can be administered orally, intravenously, or via a nebuliser. It has shown varying degrees of clinical efficacy in a variety of human diseases including respiratory tract infections due to respiratory syncytial virus and influenza, measles, herpesvirus infections, HIV infection, Lassa fever, haemorrhagic fever with renal syndrome, and (in combination with IFN-alpha) chronic hepatitis C infection. It may well prove of value against other emerging exotic infections (e.g., West Nile virus, Nipah virus).