The Toxicology of Radioactive Substances, Volume 3: Iron-59 deals with the experimental results of tests conducted at the Radiotoxicology Laboratory of the Institute of Occupational Hygiene and Disease, Academy of Medical Sciences, U.S.S.R. The book focuses on studies made on iron-59, which is widely used in science and technology, such as in the metal industry and in the research of hemoglobin metabolism in the bone marrow and red cells. Other studies show, however, that there is a long-term detrimental effect of intake of iron-59. The text then gives a brief outline of the physical, chemical, and biological properties of iron. Research also shows that the body's reaction to radioactive substances depends on how these are transmitted to the body and on their physicochemical properties. The effect of prolonged administration of radioactive iron on the electrical activity of the cerebral cortex of animals is analyzed, of which, possibly, the nervous system is most affected. The book notes also the changes in the red blood cells during chronic administration of iron-59 in small doses, wherein the hemoglobin levels increased temporarily. Studies of prolonged exposure to radioactive isotopes during pregnancy of the test animals show that there are significant changes in erythropoiesis, associated with iron deficiency. In another study, the prolonged internal administration of radioactive substances showed phasic changes in the height of electrocardiographic waves of the test animals. The text is suitable for physicists, nuclear scientists, doctors of toxicology, and researchers in nuclear medicine.