The measurement of the complex scattering parameters of DUTs with multiple inputs and outputs, so-called multi-ports, has become increasingly important in recent years. Commercial multi-port measurement systems are now available that enable the direct characterization of DUTs with four ports, some with up to eight ports, or in special versions with an even higher number of ports. Nevertheless, the classic vectorial network analyzers with two ports are still in use in many research laboratories. The research topic "Multiport Measurements" therefore deals with the investigation of methods for the precise measurement of the complex scattering parameters of multiport devices using vectorial network analyzers with two test ports and with the help of multiport network analyzers. The measurement of differential measurement objects represents another research aspect.