The fifth edition retains the essential theories of nuclear structure and stability, radioactivity and the principles of fission, fusion and breeder reactors of the earlier editions. The preparation of the more commonly used radioisotopes and their uses as tracers in research, medicine, agriculture and industry are described. The book also covers the elements of Radiation and Radiochemistry illustrated with additional examples. The section on Mössbauer effect is retained. The chapter on the detection and measurement of radioactivity is revised to include thermoluminescence and Cherenkov detectors. New additions in the present edition include a whole chapter on the separation and uses of stable and radioactive isotopes needed in bulk amounts in the atomic age. How an extension of basic principles of Nuclear Magnetic Resonance (NMR) has led to the sophisticated Magnetic Resonance Imaging (MRI), the latest diagnostic tool in medicine is discussed lucidly. Another chapter is added entitled "A Roll-call of Elementary Particles", wherein the baffling properties of quarks and gluons, with their esoteric flavours, colours, strangeness and charm are reviewed showing how their scientific characteristics tend to merge in Philosophy. The book meets the needs of Honours and Postgraduate students of Nuclear Science, Radiation and Radiochemistry.