This text is dedicated to the issues surrounding RFIC (radio-frequency integrated circuit) testing. It explains how to perform high-accuracy RF measurements of die and packages in the RF test lab. It defines the essential elements in an RF system, explains where errors can be found in such a system and shows how to mathematically remove them with calibration. This book should be of interest to: RFIC designers and high-frequency digital IC designers, IC test engineers and IC manufacturing test engineers.