Outline 5.1 Introduction 5.2 General Nature of Internal Radiation Toxicity 5.3 Internal Contamination in Human Beings 5. 5.381 Methods 5.32 Findings and Interpretation Beta Activity of the Urine Radiochemical Analysis of the Urine: Estimate of Body Burden 5.33 Source of Internal Contamination 5.34 Internal Radioactive Decontamination Therapy 5.35 Summary Internal Contamination in Animals 5.41 Methods 5.42 Findings andInterpretation Gross Observations Radioactivity of Tissues and Excreta Radiochemical Analysis of Tissues and Excreta 5.43 Autoradiographs 544 Pathology 5.45 Egg Production in Chickens Fertiity and Hatchability in Chickens 5.47 Internal Radioactive Decontamination Studies iv Chickens 5.48 Summary