The application of the Gunn effect for fast logic circuits is discussed. In particular, several new devices, such as comparators, which rely on the possibility of domain-nucleating control are described. The ultimate time-constants of these new devices can be at least one order of magnitude better than the most advanced monolithic structures with conventional transistor and diode circuitry. Finally, two circuits, namely, an adder and a shift register, incorporating these new Gunn-effect devices are proposed.