This book is intended to be used as a textbook and research reference for the field of nuclear nonproliferation. The book is primarily technical and focussed on methods of detecting clandestine nuclear material that might be illicitly transported. The book also touches on nuclear forensics, i.e. methods for identification, attribution, and establishment of transport pathways for illicit nuclear material. Also covered are topics of methods used for arms control and treaty verification, and an assessment of technologies under development for all of the above. A description of the government and international agencies involved in nuclear terrorism prevention, nuclear safeguards, and arms control is also included.