The development of powerful new techniques and refmements of tech- niques in molecular genetics in recent years, and the surge in interest in biotechnology based on genetic methods, have heralded a new golden age in molecular genetics, and stimulated in diverse disciplines much interest in the technologies themselves and their potential uses in basic and applied biomedical sciences. Although some excellent specialist laboratory manuals (especially the Cold Spring Harbor Laboratory manuals by I. H. Miller; R. W. Davies et al. ; and T. Maniatis et al. ) on certain chapters of molecular genetics exist, no general text that covers a broad spectrum of the sub- ject has thus far been published. The purpose of this manual is to pre- sent most, though of necessity not all of the important methods of molecular genetics, in a series of simple experiments, many of which can be readily accomplished by the microbiologist, biochemist or biotechnologist that has had only limited exposure to genetics. The remainder of the experiments require either greater familiarity with the subject, or guidance by someone with such experience. The book should, therefore, not only enable individuals to acquire new proce- dures for ongoing projects, but also serve as a basis for the teaching of molecular genetic techniques in formal predoctoral and postdoctoral laboratory courses.