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.