The purpose of the series on Advances in Antiviral Drug Design is to regularly review the "state of the art" on emerging new developments in the antiviral drug research field, thereby spanning the conceptual design and chemical synthesis of new antiviral compounds, their structure-activity relationship, mechanism and target(s) of action, pharmacological behavior, antiviral activity spectrum, and therapeutic potential for clinical use. Volume 2 begins with a description of the antiviral potential of antisense oligonucleotides by J. Temsamani and S. Agrawal. According to the aims of the anitsense technology, these oligonucleotides should be targeted at specific viral antisense technology, these oligonucleotides should be targeted at specific viral mRNA sequences so that translation to the virus-specified proteins is blocked; this has been achieved for a number of oligomers, some of which are now in clinical trials for the treatment of HIV, HCMV, and human papilloma virus (HPV) infections. Then C.-S. Yuan, S. Liu, S.F. Wnuk, M.J. Robins and R.T. Borchardt assess the role of S-adenosylhornocysteine (AdoHcy) hydrolase as target for the design of antiviral agents with broad-spectrum antiviral activity. This is followed by an in-depth account on the design and synthesis of a number of first-, second- and third-generation AdoHcy hydrolase inhibitors and their mode of action at the enzyme level.V.E. Marquez provides a comprehensive description of the various carbocyclic (carba) nucleosides that have been synthesized and evaluated for antiviral activity. Although the number and diversity of the carba-nucleosides that have been found to be antivirally active (or inactive) is astonishingly high, there is no limit to further expansion of this fascinating class of molecules. For the various nucleoside analogues that have to be intracellularly phosphorylated to the 5'-triphosphate stage, to interact with their target enzyme (i.e., herpesviral DNA polymerase or retroviral revers transcriptase) the first phosphorylation step is often the rate-limiting step, and thus various strategies are envisaged by C. Perigoud, J.-L. Girardet, G. Gosselin and J.-L. Bach on how to bypass this initial phosphorylation and to deliver the nucleoside 5'-monophophate directly inside the cells.The HIV protease has been considered as a paradigm for rational drug design. The enzyme is among the best understood in terms of both structure and action, and because of its crucial role in the maturation of HIV, it has been vigorously pursued as a target for anti-HIV chemotherapy. In their comprehensive review of the multidisciplinary approach towards the development of HIV protease inhibitors A.G. Tomasselli, S. Thaisrivongs and R.L. Heinrikson highlight those protease inhibitors which have been brought forward to clinical trials.