The last few years have seen the rapid development of new methodology in the field of molecular biology. New techniques have been regularly intro- duced and the sensitivity of older techniques greatly improved upon. Developments in the field of genetic engineering in particular have con- tributed a wide range of new techniques. In Volume 1, published in 1983, we introduced the reader to a selection of the more advanced analytical and preparative techniques which we considered to be frequently used by research workers in the field of molecular biology. In choosing techniques for Volume 1 we obviously had to be selective and were unable to cover as broad a spectrum of techniques as we would have liked. However, the pro- duction of Volume 2 has allowed us to develop the theme initiated in Volume 1 and also expand to include a wider range of subject areas. As with Volume 1, the majority of chapters relate to nucleic acid method- ology, but we have also covered immunological methodology and protein 1. Obviously, we purification techniques that were not included in Volume see Volume 2 as simply a continuation of Volume 1. As with Volume 1, a knowledge of certain basic biochemical techniques and terminology has been assumed. However, since many areas of molecular biology are developing at a formidable rate and constantly generating new termin- ology, a glossary of terms has been included.