This book is an up-to-date textbook for biologists and biomedical scientists covering the basics of radioisotope methodology and safety. Radioisotopes are widely used in biological and medical research, particularly in biochemistry. Graduate students and technicians usually learn how to useradioisotopes through short training courses or as part of laboratory courses in biology and biochemistry. This text was written for use in courses on the theoretical aspects of radioisotopic methods or for self-study and reference; it assumes little knowledge of radioactive materials and developsmathematical discussions slowly and clearly. The focus of the book is on the topics listed on the U.S. Nuclear Regulatory Commission's license application: principles and practices of radiation protection; radioactivity measurement, standardization and monitoring techniques and instruments;mathematics and calculations basic to the use and measurement of radioactivity; and biological effects of radiation.