Antiviral Chemotherapy has come of age. Several antiviral compounds have been formally licensed in the United States: viz. Acyclovir, for the treatment of herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections; zidovudine (azidothymidine, AZT), didanosine (dideoxyinosine, DDI), and zalcitabine (dideoxycytidine, DDC) for the treatment of retrovirus [i.e., human immunodeficiency virus (HIV)] infections; ribavirin, for the treatment of respiratory syncytial virus (RSV) infections; ganciclovir and foscarnet (phosphonoformic acid, PFA) for the treatment of cytomegalovirus (CMV) infections; and other compounds may be approved in the near future.Among various other promising antiviral compounds that are currently under development rank the capsid uncoating inhibitors, for the treatment of rhino- and other picornavirus infections, and the acyclic nucleoside phosphonates [i.e. HPMPC or (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine and PMEA or 9-(2-phosphonylmethoxyethyl)adenine] for the treatment of herpesvirus (HSV, VZV, CMV, ?) and retrovirus (HIV, ?) infections.The purpose of the series, Advances in Antiviral Drug Design, is to regularly provide an account on the chemistry of the new antiviral agents (whether licensed or en route of licensing), and to discuss their structure-activity relationship, width of activity spectrum, and mechanism of action.