Intense study of the enigmatic myc proto-oncogene over the last 20 years has broadened our view of its functions and led to insights into transcriptional regulation as well as cancer etiology, cell proliferation, apoptosis, and organismal development. How can one gene be involved in so many aspects of cellular behavior? Of particular interest is the fact that the Myc protein functions as part of a network (comprising Myc, Max, and Mad proteins) whose specific interactions direct transcriptional activation or repression of a large number of target genes. The chapters in this volume examine both molecular and biological aspects of the Myc/Max/Mad network. Included are contributions concerning the regulation of its expression, the mechanisms underlying its diverse transcriptional activities, the structural bases for its critical interactions, and the nature of its target genes. Other chapters explore the evolution of the network, its role in development and genomic instability, and the evidence for a parallel transcriptional network. Overall, this volume provides a broad and current overview of research on a crucial group of transcription factors.