Originally prepared for use as a student textbook in Radiological Defense (RADEF) courses, this manual provides the basic technical information necessary for an understanding of RADEF. It also briefly discusses the need for RADEF planning and expected postattack emergency operations. There are 14 chapters covering these major topics: introduction to radiological defense, basic concepts of nuclear science, effects of nuclear weapons, nuclear radiation measurement, radiological detection and measurement instruments, radioactive exposure rate calculations, radiological monitoring techniques and operations, protection from radiation, radiological decontamination, RADEF operations, RADEF planning, and implementing a RADEF plan. A glossary concludes the manual. (YLB)