Complete chapter headings and selected subheadings: Introduction. Organization of laboratories for radionuclide metrology. Tasks of laboratories engaged in radionuclide metrology. Definitions, Quantities, Symbols and Units: Some Useful Constants and Relations. Basic concepts and parameters used in the measurement of radioactivity. Radionuclides, radioactivity. Radiations. Energy. Dosimetry. General Problems in Radionuclide Metrology. Radiation protection. Radioactivity source preparation. Evaluation of radioactivity measurements. Detectors. Interactions of radiation with matter. Gas-ionization detectors: Ionization chambers, proportional and Geiger-Muller counters. Light-emitting, electron-emitting and solid-state detectors. Cerenkov radiation detectors. Counting radioactive atoms. Radiation energy spectrometry. Methods of Radioactivity Measurement. Relative low- and medium-geometry defined solid-angle counting; including spectrometry. 4Pi Methods. Coincidence counting. Electronic Instruments for Radioactivity Measurements. Pulses. Differentiating and integrating networks. Amplifiers; general. Microelectronics. Coincidence and anticoincidence logic circuits. Discriminators and other pulse- and data-processing equipment. Low-level-current measurements. Radioactivity Calibration Laboratory: Scope, Staff and Equipment. References.