The year 2003 marks the tenth anniversary of the first use of the acronym "Stat" (also written "STAT") in the scientific literature for a family of transcription factors which rapidly transduce cytokine-and growth factor­ elicited signals from the plasma membrane to the cell nucleus thereby activating gene transcription (thus, . s. ignal Transducers and Activators of Transcription). From those beginnings, the field of STAT transcription factors, their related regulatory molecules and their biology has grown exponentially in many different directions. In recognition of the rapid growth and broad scope of the STAT transcription factor field today, and to celebrate the tenth anniversary of the use of this term in the scientific literature, Kluwer Academic Publishers B. V. requested us to compile a volume on STAT transcription factors that could serve as an overview of this burgeoning area. Thus, we wanted a volume that would serve as a reference for what is known about STAT proteins and their biology, would describe the current state of ongoing research in this broad area, and would look toward the future to try to predict the discoveries that lie ahead. Our charge was to seek out the very best experts in the field and to coax them to briefly summarize their areas of expertise.