The need to measure electrical power is common to many branches of science and engineering. This book presents a wide-ranging survey of the many types of radio-frequency and microwave power meter and the techniques which are used for calibrating and intercomparing them. The frequency range is 1 MHz to 200 GHz. The first of the sixteen chapters considers the fundamentals. Four chapters are then devoted to the subject of calorimetry, which forms the basis of the majority of primary standards for power measurement. A further five chapters describe the various types of non-calorimetric power meter, which include not only the commonly used thermistor, thermoelectric and diode types, but also force-operated instruments and a considerable number of miscellaneous devices. Calibration and intercomparison methods are covered in three closely linked chapters which treat respectively the basic techniques, the use of reflectometers for power meter calibration, and the problems associated with connectors and adapters. In the last three chapters a mixture of topics is covered. First a concise survey of pulsed power measurements is presented. Attention is then given to the topics of voltage and current measurement, which are closely related to power measurement. Finally, the subject of the international intercomparison of standards is discussed and the results of some of the more important intercomparison exercises are summarised.