Antiviral chemotherapy has come of age, and, after an initial slow pro­ gress, the development of new antiviral agents has proceeded at a more rapid pace and the perspectives for their clinical use have increased considerably. Now, 25 years after the first antiviral assay (idoxuridine) was introduced in the clinic, it is fitting to commemorate the beginning of the antivirals' era. In its introductory chapter B.E. Juel-Jensen touches on what may be considered as five of the most fundamental requirements of an antiviral drug : efficacy, relative non-toxicity, easy solubility, ready availability and reasonable cost. Surely, the antiviral drugs that have so far been used in the clinic could still be improved upon as one or more of these five essential demands are concerned. How is all began is narrated by W.H. Prusoff. The first antiviral drugs to be used in humans were methisazone and idoxuridine, the former, which is now of archival interest, in the prevention of smallpox, the latter, which was approved for clinical use in the United States in 1962, for the topical treatment of herpetic keratitis. In terms of potency, also because of solubility reasons, idoxuridine has been superseded by trifluridine in the topical treatment of herpes simplex epithelial keratitis. H.E. Kaufman did not find trifluridine or acyclovir ef­ fective in the treatment of deep stromal keratitis or iritis and he reckons that other antiviral drugs (i.e. bromovinyldeoxyuridine) would not be effec­ tive either.