The behaviour of waveguiding structures loaded with solid-state semiconductors under an external DC magnetic field is considered. The solid-state physical basis for the semiconductor magnetoplasma effect is presented, including carrier transport, Drude model, linearised governing equations and conductivity tensor. The resulting asymmetric anisotropy in the complex-element permittivity tensor can be exploited to generate nonreciprocal propagation. Dynamic numerical methods used to obtain the propagation characteristics of various waveguiding structures, including rectangular, circular and planar (i.e. microstrip, coplanar, slotline and finline) are presented. The frequencies covered extend from about about 9 GHz in the microwave regime up through the millimetre, submillimetre and optical regions.