This p Ublication contains the Review Lectures presented at a joint NATO Advanced Study Institute and FEES Advanced Study Course held at Les Arcs, Bourg-8aint-Maurice, France, from the 19th June – 2nd July 1983. The Course, entitled "Targets for the Design of Antiviral Agents" was in some ways a sequel to the NATO-FEES Course held at SOGESTA (near Urbino), Italy from the 7th – 18th May 1979 and published as volume A26 in this series. During the subsequent four years, we have witnessed the first of the "new generation" of antiviral compounds, which are more efficacious and less toxic than the "classical" antiviral drugs, reach the clinic and we felt that it w~s the right time to assess the future prospects of this ver Y important and exciting field. The vast majority of the drugs developed recently have proved active against various members of the herpesvirus family and elsewhere in this publication we learn that the cure for only rather few viral diseases, such as the common cold, influenza and herpes, promises the return on investment required by the pharmaceutical industry. However, the aim of this Course was for eminent virologists to identify possible targets among the various virus classes against which the chemists could then design suitable therapeutic agents. Recent advances with antiherpesvirus drugs have shown that a far greater selectivity and therapeutic index can be obtained than was previously thought to be possible.