Over the last 15 years, there has been renewed interest in supercritical fluids owing to their unique properties and relatively low environmental impact. Greatest attention has been given to the extraction and separation of organic compounds. Supercritical fluids have also been successfully used for particle production, as reaction media, and for the destruction of toxic waste. Supercritical carbon dioxide has been the most widely used supercritical fluid, mainly because it is cheap, relatively ntoxic, and has convenient critical values. Supercritical fluids have also been used on analytical and preparative scales for many biological and other applications. Many papers have been published on the use of supercritical fluids. However, few have acted as a detailed instruction manual for those wanting to use the techniques for the first time. We anticipate that this Methods in Biotechlogy volume, Supercritical Fluid Methods and Protocols will s- isfy the need for such a book. Every chapter has been written by experienced workers and should, if closely followed, enable workers with some or previous experience of supercritical fluids to conduct experiments successfully at the first attempt.