Introduction 21.2 The Medical Research Council Common Cold Unit 21.3 Clinical need for antivirals 21.3.1 Epidemic influenza 21.3.2 Serious lower respiratory tract infections caused by respiratory syncytial virus 21.3.3 Viruses causing upper respiratory tract infection 21.3.4 The chemistry of inhibitors of respiratory viruses 21.4 Influenza 21.4.1 Amantadinethe first antiinfluenza A virus drug 21.4.2 General recommendations for the clinical use of amantadine 21.4.3 'Designed' anti-neuraminidase drugs 21.5 Respiratory syncytial (RS) virus 21.5.1 Inhibition by ribavirin 21.6 Rhinoviruses 21.6.1 Antiviral drugs interacting with virus structural proteins 21.6.2 Virion-binding drugs acting against rhinovirus infections 21.7 Conclusions 21.8 References Viral and Other Infections of the Human Respiratory Tract. Edited by S. Myint and D. Taylor-Robinson.