Book excerpt: The basic theory and analytical methods used in the development of accurate microwave measurement methods and standards are presented. Developments at the U.S. National Bureau of Standards during 1948-1968 are described in which the above theory and analytical methods were applied. These developments were in the fields of power, impedance, attenuation and phase shift, and led to the establishment of National Standards and calibration methods at frequencies from about 300 MHz to 30 GHz. (Author).