The transcription factor NF-kappaB and the signaling pathways regulating its activity constitute a paradigm of membrane to nucleus communication. NF-kappaB is central to a number of cellular functions including cell proliferation, apoptosis, and cellular differentiation. This transcription factor also plays essential roles in innate and acquired immunity, and its deregulation leads to important human diseases such as inflammation and cancer. Therefore NF-kappaB, together with the signaling pathways leading to its activation, constitute an attractive therapeutic target. This book is the first to review and synthesize our knowledge on this interesting transcription factor. It will be of great interest for those entering or already actively working in the NF-kappaB field, as well as a valuable reference for students, established researchers, or clinicians with wider interests in the fields of molecular cell biology and biomedicine.