The present work reviews microwave-assisted heterogeneous gas-phase catalysis. This special form of non-classical energy input by microwave radiation still represents a peripheral area of catalysis, alternative reaction ways, and of chemical and process engineering, with growing academical and industrial attractiveness. Experimental set-ups described in literature are critically regarded and hints to create more useful multimode microwave reactors are given. Historical developments, current tendencies, and a short introduction to the theory of dielectric heating are pointed out.