Only in recent years has the field of antiviral therapy come of age. Despite tremendous advances in the treatment of bacterial infections from the 1940s through the 1960s, therapeutic interventions for viral diseases largely eluded medical researchers during this same period. The primary reason for this failure rested in the belief that the molecular mechanisms of viral and cellular nucleic acid replication and protein synthesis were so closely intertwined that one could not disable viral replication without severely damaging the host cell. The discovery of acyclovir, with its initial activation using the virus-encoded thymidine kinase, dispelled this belief and ushered in the increasingly rapid advances in antiviral therapies that have been experienced during the past 20 years. This article discusses all antiviral compounds licensed by the Food and Drug Administration during the past decade, with the exception of compounds that treat influenza and human immunodeficiency virus infections. Copyright © 2001 W.B. by Saunders Company.