The purpose of Ribozyme Protocols is to provide a helpful compilation of protocols that will be of use¿^not only to those with some experience of ribozymes¿^but also to those wishing to use ribozymes for the first time. Although it is usually impossible to cover every aspect of a scientific field, I believe this book approaches that ideal and should help all readers perform meaningful experiments using ribozymes. To design ribozymes, one must consider whether the target site will be accessible; this task can be facilitated by using computer programs that pre­ dict the folding of the target RNA. Such programs are detailed in Chapters 2 and 3. If the chosen target is an RNA virus that can mutate rapidly, it makes sense to consider those parts of the genome that are least likely to change during viral replication. An example of how this can be done is described in Chapter 4. Although computer analysis may be a useful starting point to select tar­ get sites, there seems, at the moment, to be no guarantee that any particular chosen site will be efficiently cleaved. Some workers have deliberately bypassed this problem by using libraries of ribozyme sequences and by select­ ing those that actually hybridize to and/or cleave the target; these methods are described in Chapters 5 and 6.