Intended for final year undergraduate and postgraduate students in molecular biology and biochemistry, this book discusses in detail information currently available on transcription factors, emphasizing common motifs, themes and mechanisms. It summarizes the major families, describes the mechanics of activation and repression of eukaryotic genes by transcription factors, and explains the relationship between the structure and function of these factors. Furthermore, it highlights the importance of transcription factors during the development, differentiation and transformation of eukaryotic cells, and provides the principles behind the methods employed to study transcription factors in vivo and in vitro.