Other than classified publications, this technical monograph is perhaps the only text that addresses the topic of “Basic Intelligence.” The lack of scholarly treatments on Basic Intelligence demonstrates that the subject has been ignored in the intelligence studies literature. This monograph, therefore, breaks new ground by presenting a concise discussion of the topic. The word “basic” describes something fundamental or something that forms the base for further development or establishes the underlying foundation to what could later be enhanced. When it comes to Basic Intelligence, one might naturally assume that this intelligence category is rudimentary. But it is not. Basic Intelligence is a distinct type of intelligence that requires planning and consideration like the other categories of intelligence—strategic, operational, and tactical. Basic Intelligence is used in background briefings, evaluations, assessments, estimates, and counterintelligence investigations. In this fifth in the series of “Espionage Black Books,” Dr Henry Prunckun examines what Basic Intelligence is, how it fits into the broader framework of intelligence practice, the policies and procedures involved in collecting and archiving Basic Intelligence, and the standards used to assess the reliability and validity of these data.